North American Recent Soft-shelled Turtles (Family Trionychidae)

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Title: North American Recent Soft-shelled Turtles (Family Trionychidae)
Author: Webb, Robert G.
Language: English
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UNIVERSITY OF KANSAS PUBLICATIONS

MUSEUM OF NATURAL HISTORY

Volume 13, No. 10, pp. 429-611, pls. 31-54, 24 figs.

February 16, 1962

North American Recent Soft-shelled Turtles

(Family Trionychidae)

ROBERT G. WEBB

UNIVERSITY OF KANSAS

LAWRENCE

1962

UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY

Editors: E. Raymond Hall, Chairman, Henry S. Fitch, Robert W. Wilson

Volume 13, No. 10, pp. 429-611, pls. 31-54, 24 figs.

Published February 16, 1962

UNIVERSITY OF KANSAS

Lawrence, Kansas

PRINTED IN

THE STATE PRINTING PLANT

TOPEKA, KANSAS

1962

[Illustration (Union Label)]

28-7818

North American Recent Soft-shelled Turtles

(Family Trionychidae)

ROBERT G. WEBB

CONTENTS

PAGE

CONTENTS 431

INTRODUCTION 433
Collecting Methods 434
Materials and Procedure 437
Acknowledgments 439

TAXONOMY 439
Family Trionychidae Bell, 1828 439
Genus _Trionyx_ Geoffroy, 1809 443
Variation 445
Secondary Sexual Variation 446
Ontogenetic Variation 449
Geographic Variation 453
Character Analysis 460
Composition of the Genus _Trionyx_ in North America 476
Artificial Key to North American Species and Subspecies
of the Genus _Trionyx_ 476
Systematic Account of Species and Subspecies 479
_Trionyx ferox_ 479
_Trionyx spinifer_ 486
_Trionyx spinifer spinifer_ 489
_Trionyx spinifer hartwegi_ 497
_Trionyx spinifer asper_ 502
_Trionyx spinifer emoryi_ 510
_Trionyx spinifer guadalupensis_ 517
_Trionyx spinifer pallidus_ 522
_Trionyx ater_ 528
_Trionyx muticus_ 531
_Trionyx muticus muticus_ 534
_Trionyx muticus calvatus_ 539

NATURAL HISTORY 541
Habitat 541
Daily and Seasonal Activity 547
Diurnal Habits 547
Behavior Adaptations 549
Movement 552
Nocturnal Habits 553
Seasonal Occurrence 553
Food Habits 555
Reproduction 558
Size of Males at Sexual Maturity 558
Size of Females at Sexual Maturity 560
Sexual Activity 563
Deposition of Eggs 565
Reproductive Potential 568
Eggs 572
Incubation and Hatching 573
Age and Growth 574
Mortality 576
Parasites 576
Economic Importance 577

EVOLUTIONARY HISTORY 578
Distribution 578
Relationships 579
Fossils 582
Phylogeny 585
The Importance of the Study of Turtle Populations in
Relation to the History of River Systems 588

SUMMARY 590

LITERATURE CITED 594

INTRODUCTION

Is it true that the greater the degree of resemblance between two
populations the shorter the time the two have been spatially isolated?
Are aquatic environments more stable than terrestrial environments?
These questions occurred to me while I was collecting turtles from river
systems of the Gulf Coast. As a general rule, each kind of turtle seemed
to occur throughout one continuous river system or large tributary, and
with no barriers to dispersal therein and with the lapse of enough time
for a population to reach its limits of dispersal, the question arose,
"Where do subspecies and zones of intergradation occur?" It seemed
logical to think that each isolated and continuous aquatic environment
would not contain more than one subspecies of the same species. In
terrestrial environments subspecies and transitions between them were
recognizable. Terrestrial habitats were continuous for longer distances
than the isolated, aquatic habitats. But, different species of turtles
prefer different kinds of aquatic habitats. Also, barriers occur in
large drainage systems, such as the Mississippi, where, in general,
the western tributaries are sluggish, turbid and shallow, and the
eastern tributaries are fast-flowing, clear and deep. But in young,
relatively small, river systems that do not traverse radically different
physiographic regions, and that show no gross ecological differences,
habitats or microhabitats that do exist probably are only partial
barriers and seem not to prevent the dispersal of most kinds of aquatic
turtles. Consequently, it seemed that study of the degree of difference
between closely related populations of turtles that occurred in one
drainage system, or in adjacent drainage systems would indicate the
length of time, respectively, that the drainage system had been
continuous or the length of time that two or more systems had been
isolated from one another.

Rivers or series of river systems having endemic kinds of turtles or
having the most kinds of turtles that are different from those in
adjacent rivers may be the oldest geologically, or may have been
isolated the longest. Knowledge of the kinds of turtles and their
relationships and distribution could indicate chronological changes in
aquatic habitats. Of course, modifying factors such as differences
between populations of turtles in rates of evolutionary change, degrees
of vagility, rates of dispersal, and overland migrations need to be
taken into account.

My accumulation of data on soft-shelled turtles was begun in the early
nineteen-fifties. Although American softshells have been discussed in a
revisionary manner by Agassiz (1857), Siebenrock (1924), Stejneger
(1944) and Neill (1951), the relationships of all the component
populations have not hitherto been appreciated. The present account
attempts to combine in one publication what is known concerning the
taxonomy, geographic distribution, life history, and relationships of
the Recent American species and subspecies of the genus _Trionyx_.

Collecting Methods

Nocturnal collecting, by hand, from a boat that was nosed among brush
piles along the shore line of rivers (Chaney and Smith, 1950:323) in the
early 1950's on rivers of the Gulf Coast drainage east of Texas yielded
many turtles of the genus _Graptemys_ but few softshells. Chaney and
Smith (_loc. cit._) reported only one softshell among 336 turtles taken
in 21 collecting hours on July 5, 6 and 7 on the Sabine River; Cagle and
Chaney (1950:385), however, recorded 11.6 per cent softshells of 208
turtles (collecting time not stated) taken on the Caddo Lake Spillway in
Louisiana. Using hoop-nets is probably the most efficient method for
collecting softshells considering the time and effort involved, and is
the chief method I have used. Lagler (1943a:24) mentioned the use of
watermelon rind as an effective bait. Kenneth Shain (field notes)
trapped _T. spinifer emoryi_ in hoop-nets baited with bread. I have used
chopped fresh fish with most success; canned sardines have also been
satisfactory. These baits seem to be more successful for trapping
_spinifer_ than they are for _muticus_. Hoop-nets were used to trap
turtles in Lake Texoma, Oklahoma, from June 14 to July 2, 1954. The
number of traps (usually four, rarely five) and trapping success varied
with location. Of 156 turtles, 19 (12%) were _T. spinifer_ and one was
_T. muticus_.

Trotlines and set lines frequently catch softshells; sport fishermen
often complain of catching these turtles on hook and line. Live worms,
soft-bodied insects, small crawfish, minnows, small pieces of fish and
other kinds of meat are adequate bait. Capture depends on the skill of
attachment of the bait and the size of hook used. In my experience,
softshells (mostly _spinifer_) were taken on trotlines that were set in
lakes or the slower-moving parts of rivers a few inches below the
surface. I have records of only two _muticus_ taken on trotlines.
Goin (1948:304) stated that commercial fishermen catch softshells on
trotlines set for catfish on the bottom of river beds. Evermann and
Clark (1920:595) found softshells to be caught more often than any
other kind of turtle in traps, on set lines, and by anglers in Lake
Maxinkuckee, Indiana. Some residents of the South tell of so placing
baits that turtles are lured to tread water against an object set with
recurved hooks upon which the webbing of the forelimbs are impaled.

Individuals of _muticus_ and _spinifer_ frequently bury themselves in
sand in shallow water and can be collected by hand by noting swirls or
disturbances on the bottom caused by a turtle withdrawing its head
(Conant, 1951:156, 159). Professional turtle collectors take them by
"noodeling" (Conant, _op. cit._:160); Lagler (1943a:22) elaborated on
the method of "noodling." P. W. Smith (1947:39) remarked that 20 or more
softshells were taken "within a few hours by probing sand bars at the
water edge" near Charleston, Illinois. From a distance I observed an
individual of _T. s. asper_ bury itself in shallow water on the Escambia
River, Florida. Small individuals of _muticus_ have been taken by hand
along the shore of Lake Texoma. Along the Flint River near Bainbridge,
Georgia, two hatchlings that were buried in sand in shallow water
emerged at my approach and scurried a few inches, then buried themselves
again. Larger turtles seem to be more wary. One that was disturbed,
emerged from the sand and swam toward deep water.

In clear water, water-goggling may be effective in securing softshells.
Marchand (_in_ Carr, 1952:417-18) mentioned that softshells (_ferox_)
can be found buried in deep water with only the heads visible; the
turtles are not easily frightened under water and may be captured by
grasping their necks. A similar technique described by Allen and Neill
(1950:3) resulted in the capture of trionychid turtles. In clear water
of the White River, Arkansas, I collected a few softshells by hand as
they lay on the bottom.

In shallow-water areas of large rivers, lakes and tributaries, seining
often procures softshells. Methods used in fisheries investigations such
as the application of rotenone and electric shockers, and even
dynamiting, sometimes yield soft-shelled turtles. Carr (1952:419) wrote
that numbers of _ferox_ were incapacitated by rotenone in Florida lakes,
although no other species of turtle was affected. I captured a snapping
turtle (_Chelydra serpentina_) that was immobilized by the current from
an electric shocker in a small, alga-choked tributary of Cache Creek,
Comanche County, Oklahoma; presumably turtles must come in close contact
with the electrodes to be affected (see discussion by Gunning and Lewis,
1957:52).

The effectiveness of gill nets in trapping turtles is indicated by
information kindly supplied by Mr. Alfred Houser on gill-net operations
from July through December, 1952, under the direction of Mr. "Bud"
Oldham, a commercial fisherman. The 4-inch mesh nets were in Lake Texoma
at the mouth of Briar Creek, two miles south of Powell, Marshall County,
Oklahoma, in 25 to 30 feet of water. Eighty to 90 per cent of the
turtles secured were softshells; more were taken near shoreline than
away from shore even though the depth was about the same. An average of
only one turtle every four days was taken in July and August when the
turtles presumably are most active (Table 1). One gill-net day is
equivalent to one gill net, 200 yards long, operated for 24 hours.

TABLE 1. The Abundance of Turtles as Revealed by Gill-net
Operations in Lake Texoma, 1952.

===========+==========+===========+===============
| Gill-net | Number of | Gill-net days
MONTH | days | turtles | per turtle
-----------+----------+-----------+---------------
July | 835 | 213 | 3.9
August | 816 | 199 | 4.6
September | 743 | 42 | 17.7
October | 1661 | 82 | 20.3
November | 1322 | 48 | 27.5
December | 864 | 5 | 172.8
-----------+----------+-----------+---------------

Dr. Virgil Dowell, while making fishery studies two miles east of
Willis, Marshall County, Oklahoma, caught, on the average, 1.5 turtles
per day. Of 75 turtles collected from July 1 through October 18, 1953,
66 were _Trionyx_ (_spinifer_ and _muticus_), five were _Graptemys_ and
four were _Pseudemys scripta_. No more than two gill nets were used
simultaneously. The nets were moved from time to time and varied in
dimensions, but those used most of the time were 200 feet long and eight
feet deep with a 3-inch mesh.

The few captures by Houser probably resulted from long-continued
trapping in one place; the gill nets were not moved in the entire
six-month period or for some time previously. Breckenridge (1955:6)
commented on the sedentary nature of _spinifer_ (in Minnesota) and
quoted a professional turtle trapper as stating that "after a section of
a river has been trapped heavily for softshells, little success can be
expected in that area for as much as three or four years thereafter."
Both Houser's and Dowell's data indicate a higher percentage of
soft-shelled turtles collected than any other species. The number
caught probably depends, at least partly, on the food habits of the
species and is influenced by the enmeshed fish, which, serving as a food
source, attract the turtles.

Materials and Procedures

In the course of this study I examined 1849 soft-shelled turtles,
including some incomplete alcoholic or dried specimens, such as those
represented only by skulls or by other osteological material. Material
was examined from each of the collections named below (except KKA), and
these are mentioned in the text by the following abbreviations:

AMNH American Museum of Natural History
ANSP Academy of Natural Sciences, Philadelphia
BCB Bryce C. Brown, private collection, Baylor University
CM Carnegie Museum
CNHM Chicago Natural History Museum
INHS Illinois Natural History Survey, University of Illinois
KKA Kraig K. Adler, private collection, data in letter dated January 8, 1960
KU Museum of Natural History, The University of Kansas
LSU Louisiana State University
MCZ Museum of Comparative Zoology, Harvard College
MSU The Museum, Michigan State University
NHB Naturhistorisches Museum Basel, Switzerland
OU University of Oklahoma Museum, Division of Zoology
SM Strecker Museum, Baylor University
TCWC Texas Cooperative Wildlife Collection, Texas Agricultural and Mechanical College
TNHC Texas Natural History Collection, The University of Texas
TTC Texas Technological College
TU Tulane University
UA University of Alabama
UI Museum of Natural History, The University of Illinois
UMMZ Museum of Zoology, The University of Michigan
USNM United States National Museum
WEB William E. Brode, private collection, Mississippi Southern College
WTN Wilfred T. Neill, private collection

External measurements (listed under the section, "Variation") were
taken by the writer by means of a Vernier caliper or a steel tape.
Measurements of the skulls are in millimeters and tenths as taken by
the writer with dial calipers. Partial wrinkling of the carapace at
the edges of some specimens causes some error in measurements;
consequently, length of plastron is used as the measurement of
reference.

Scattergrams based on external measurements were constructed. Some
demonstrate considerable ontogenetic variation. An inspection of the
scattergrams indicated regressions essentially linear in nature, but
sometimes occasioned an arbitrary separation of samples into size
groups to show ontogenetic variation; no secondary sexual differences
could be discerned. Several ratios were developed from the
measurements. The data correspond to the regression model 1A in
"Statistical Methods" (Snedecor, 1956, sec. 6.13); consequently, the
sample ratios indicate the slope of regression and are useful in
comparisons. Sample-means and their estimated standard errors are
compared graphically to show general trends in proportional
characters. Comparisons of means and standard errors indicate
statistical significance between populations if the sample-means plus
or minus twice their standard errors do not overlap, but this method
of comparison is valid only when comparing two samples (Pimentel,
1959:100).

In the section on "Variation," general features applicable to all
kinds of soft-shelled turtles are discussed under the following
headings: secondary sexual, ontogenetic, and geographic; individual
variation is mentioned in accounts of species and subspecies. In the
section "Character Analysis" external and osteological characters
having taxonomic significance are discussed.

Vernacular names follow, as closely as possible, those recommended by
the Committee on Herpetological Common Names (1956). The synonymy of
each monotypic species or subspecies begins with the name as given in
the original description. The second entry is the name-combination
herein applied to the taxon. Other entries are first usages, in
chronological order, of other names (synonyms) that have been applied
to the taxon in question. Next, the type is briefly discussed followed
by the "Range" defined in general geographic terms, and, when
appropriate, in terms of river drainage systems. "Diagnosis" includes
a combination of characters that facilitates quick identification. In
polytypic species, the diagnosis of a subspecies is designed only to
distinguish it from other subspecies of that species. The comments
included under the subsection entitled "Description" pertain to
individuals from an area where the taxon is most clearly
differentiated. Because osteological characters are significant only
at the specific level, they appear under the accounts of each species
(excluding _ater_). Proportional characters as given in the
"Diagnosis" are only in general terms; more specific data are set
forth in the subsection, "Description" or in the various text figures,
mostly in the section on "Variation," page 445. Proportions pertaining
to the species _muticus_ were derived only from the nominal
subspecies, and appear under the account of the species. A subsection
"Variation" under the accounts of some subspecies includes information
concerning principally individual variation and coloration; because
color is not considered to be of major taxonomic importance, color
terms are used without reference to any standard color guide. The
subsection "Remarks" follows the section on "Comparisons," and may
include comments on nomenclature, intergradation and other information
related to the distribution or taxonomy of the subspecies.

The probable geographic range of each species and subspecies is shown
on one of the maps. Locality records of specimens that I have examined
are shown by solid circles. Additional records of occurrence
(published records or specimens otherwise not seen) are shown by
hollow circles. Localities only a short distance apart share the same
circle.

Under the subsection "Specimens examined," a number in parentheses
following a museum number indicates the number of specimens referable
to that museum number. All localities of specimens examined are
indicated on one of the maps. The list of specimens is arranged
alphabetically by states (Canadian provinces precede states of the
United States under the account of _T. spinifer spinifer_, and Mexican
states follow those of the United States under _T. s. emoryi_),
alphabetically by counties, and within a county alphabetically by
abbreviations of museums; then, museum catalogue numbers are arranged
consecutively. Records in the literature are not included if they
refer to the same locality from which at least one specimen has been
examined, or refer to a less restricted locality that includes the
area from which at least one specimen has been examined. Localities
within a county are arranged alphabetically by author; the appropriate
reference may follow several localities.

All generic, specific and subspecific names (but not all the different
kinds of name-combinations) that have been applied to American
soft-shelled turtles are listed in a subsection entitled "Synonymy"
under the heading "Genus Trionyx Geoffroy, 1809."

Acknowledgments

Completion of this study has been made possible only by the
co-operation of those persons in charge of the collections listed
above and I am grateful to them for the privilege of examining
specimens. Also I wish to thank Dr. E. Raymond Hall for the facilities
afforded by the Museum of Natural History at the University of Kansas,
as well as for editorial assistance in the preparation of the
manuscript, and especially Dr. Henry S. Fitch under whose guidance
this research was carried out.

In addition to various staff members, graduate students, and
individuals whose help is acknowledged at appropriate places in the
text, Dr. Rollin H. Baker, Dr. Fred R. Cagle, Mr. J. Keever Greer, Dr.
A. Byron Leonard, Dr. Carl D. Riggs, and Dr. Edward H. Taylor deserve
especial mention for aid extended in the course of this study. I am
indebted to Mr. J. C. Battersby, British Museum (Natural History),
London, for information concerning the type of _Trionyx ferox_, to Dr.
Jean Guibé, Museum d'Histoire Naturelle, Paris, for information
concerning the types of _Trionyx muticus_, _T. spinifer_ and _T.
carinatus_, and photographs of the types of _T. muticus_, _T.
spinifer_ and _T. ocellatus_, and to Dr. Lothar Forcart of the
Naturhistorisches Museum, Basel, Switzerland, for information
pertaining to a published record of _T. muticus_.

The maps and figures are the work of Miss Lucy Jean Remple and Mrs.
Lorna Cordonnier, University of Kansas. Dr. John M. Legler, University
of Utah, prepared most of the photographs on plates 1-20; photographs
as mentioned in the preceding paragraph were received from Dr. Guibé,
one was provided through the co-operation of Roger Conant and Isabelle
Hunt Conant, another was furnished by Mr. J. Keever Greer, and the
others were taken by me. Field work was financed in part by funds
provided by the Sigma Xi-RESA Research Fund.

TAXONOMY

Family Trionychidae Bell, 1828

Recent soft-shelled turtles comprise a well-defined assemblage of the
family Trionychidae. Although the scope of this study does not involve
an assay of the relationships of the soft-shelled turtles of the Old
World, a brief résumé that includes some of the salient characteristics
of the family is included.

_Diagnosis._--Articulation between last cervical and first dorsal
vertebrae by zygopophyses only; preplastra separated from hyoplastra
by /\-shaped epiplastron, entoplastron absent (Williams and McDowell,
1952:263-75); marginal bones absent or forming an incomplete series,
not connected with ribs that extend beyond pleural plates; claws on
only three inner digits; fourth digit having four or more phalanges;
plastron united to carapace by ligamentous tissue (Smith, 1931:147).

_General characters._--Size large, "... some attaining probably 5 feet
in length of carapace" (Boulenger, 1890:10); body depressed; carapace
and plastron lacking horny epidermal shields, covered instead with
soft skin; snout ending in fleshy, tubate proboscis; jaws concealed by
fleshy lips; tail short; digits well-webbed; cervical vertebrae
opisthocoelous (eighth having double articulation in front); neck
elongate, cervical region equaling or exceeding length of dorsal
vertebral column; head and neck completely retractile, bending by
means of sigmoid curve in vertical plane; ear hidden; skull elongate,
having three posterior projections (median one produced by
supraoccipital and two lateral projections formed chiefly by
squamosals); temporal region emarginate posteriorly, forming wide
shallow fossa; premaxillae fused; an intermaxillary foramen;
pterygoids separated by basisphenoid that contacts palatines; vomer,
if present, not separating palatines; pelvis not fused to carapace and
plastron; plastron reduced, a median vacuity usually present; plastral
bones developing sculpturing with increase in size, forming four to
seven so-called plastral callosities; carapace with or without
prenuchal bone; nuchal overlapping or overlapped by first pleural;
neurals in continuous series or interrupted by pleurals; bony plates
of carapace sculptured; mandible having well-developed coronoid bone;
cutaneous femoral valves that conceal hind limbs present or absent;
two or three pairs of scent glands; cloacal bursae absent (Smith and
James, 1958:89); forelimbs having antebrachial scalation; body of
hyoid apparatus formed of two or three pairs of bones; penis broad,
expanded and pentifid, sulcus spermaticus quadrifid having branches in
each of four lateral projections (Hoffman, 1890:298, pl. 47, fig. 2);
aquatic, principally in fresh water; mainly carnivorous; flesh of many
species eaten. (See Boulenger, 1889:237-41; Loveridge and Williams,
1957:412; Romer, 1956:513; Smith, _op. cit._:147-54).

_Recent distribution_ (Figure 1).--North America, from extreme
southeastern Canada and eastern United States west to Rocky Mountains
and south to northern México; introduced in southwestern United States
(Conant, 1958:69-73). Africa, from Egypt and Senegal south to Angola
and Zambesi River drainage (Loveridge and Williams, _op.
cit._:412-68); occurrence of _Trionyx triunguis_ in Syria (Boulenger,
_op. cit._:255) and coastal streams of Palestine (Schmidt and Inger,
1957:36) considered accidental by Flower (1933:753-54). Southwestern
Asia (Tigris and Euphrates River drainage) in eastern Turkey, Syria,
Iraq and northeastern Israel (Mertens and Wermuth, 1955:388).
Southeastern Asia, from Pakistan and India (Indus River drainage) and
Manchuria and adjacent Siberia (Amur River drainage) to Ceylon, Japan,
Formosa, Hainan, Luzon, Sumatra, Java, Borneo, Timor and southeastern
New Guinea (De Rooij, 1915:325-32; Okada, 1938:108; Pope, 1935:60-64;
Smith, 1931:158-79; Stejneger, 1907:514-532; Taylor, 1920:141).

_Trionyx cartilagineus_ is questionably recorded from the Moluccas (De
Rooij, _op. cit._:330). _T. sinensis_ has been introduced on Kauai
Island, Hawaiian Islands (Brock, 1947:142; Oliver and Shaw, 1953:83),
one of the Bonin Islands (Okada, 1930:187-94), and probably Timor (De
Rooij, _op. cit._:331). All insular records east of Borneo and Java
are probably the result of introductions, except perhaps those of
_Pelochelys_ on Luzon and New Guinea (Darlington, 1957:210).

[Illustration: FIG. 1. Geographic distribution of the family
Trionychidae.]

_Recent genera._--According to Mertens and Wermuth (1955:387-95), there
are 21 species belonging to six genera as follows:

_Chitra_ Gray, 1844 (1)
_Cyclanorbis_ Gray, 1854 (2)
_Cycloderma_ Peters, 1854 (2)
_Lissemys_ Smith, 1931 (1)
_Pelochelys_ Gray, 1864 (1)
_Trionyx_ Geoffroy, 1809 (14)

_Dogania_ is considered a synonym of _Trionyx_ (Loveridge and Williams,
_op. cit._:422).

_Geologic range._--Lower Cretaceous (possibly Upper Jurassic) to Recent
of Asia; Upper Cretaceous to Recent of North America; Paleocene (Upper
Jurassic, assuming _Trionyx primoevus_ is a trionychid) to Pleistocene
of Europe; Lower Miocene to Recent of Africa; Pleistocene to Recent in
East Indies (Loveridge and Williams, _op. cit._:412; Romer, 1945:594);
questionable trionychid fragments from Pleistocene of Australia
(Darlington, _loc. cit._). $/

_Remarks._--The genera _Lissemys_, _Cyclanorbis_ and _Cycloderma_ are
distinguished from _Pelochelys_, _Chitra_ and _Trionyx_ by several
characters (Loveridge and Williams, _op. cit._:414). The recognition of
two groups of genera caused Deraniyagala (1939:290) to erect two
families, Cyclanorbidae and Trionychidae. An appraisal of fossils
prompted Hummel (1929:768) to propose two corresponding subfamilies,
Cyclanorbinae and Trionychinae. Williams (1950:554) considered the two
groups as subfamilies (Lissemydinae and Trionychinae).

Baur (1887:97) regarded the Trionychidae as constituting a separate
suborder distinct from the rest of the living turtles. Later (1891),
however, he pointed out the resemblances of the Trionychidae and
Carettochelyidae (having one living genus in New Guinea), and the
cryptodiran affinities of _Carettochelys_. Bergounioux (1932:1408)
mentioned the close resemblance of the Carettochelyidae to _Trionyx_ but
considered the former as having pleurodiran affinities, a view adopted
by Deraniyagala (_loc. cit._). Most students now consider the two
families to be closely related, and conceive of both as members of the
suborder Cryptodira (Hummel, 1929:768; Williams, _loc. cit._; Mertens
and Wermuth, 1955).

The oldest trionychid fossil, _Trionyx primoevus_, is from marine
deposits of the Upper Jurassic (Kiméridgien) from "Cap de la Hève," and
its characters do not indicate the kind of cryptodiran ancestor from
which the family arose (Bergounioux, _op. cit._:1409; 1937:188). Lane
(1910:350) found that the entoplastron (= epiplastron) was paired in
embryos of _Trionyx_ and regarded that genus as the most primitive of
the order; he also mentioned Wiedersheim's report of rudiments of teeth
in embryos of _Trionyx_. Baur (1891:637-38) thought that the family
arose directly from the Amphichelydia, that the ancestors of the
Trionychidae closely resembled _Carettochelys_ in the structure of the
carapace and plastron, and that a progressive reduction in ossification
of those structures occurred. Nopcsa (1926:654) also wrote that the
family originated from ancestors having a well-developed plastron; he
maintained that the progressive reduction in ossification of the
plastron was a specialization for aquatic life, and that the more
primitive trionychids had the best developed bones and callosities.
Hummel (1929:772) also thought that there had been a progressive
reduction in ossification. Bergounioux (1932:1408; 1936:1088,
1952:2304), on the contrary, thought that there had been a progressive
increase in ossification of the marginal bones in both families as well
as of the plastron (1936:1088; 1937:190). Zangerl's study of the shell
elements of turtles (1939:393) indicated that _Trionyx_ was highly
specialized in having a well-developed epithecal armor (sculptured
callosities, neurals and costals), and that it occurred in most aquatic
turtles; the development in soft-shells suggested that members of the
family had maintained an aquatic mode of life over a long period of
geologic time, a view supported by Deraniyagala (1930:1066). Of interest
are Stunkard's remarks (1930:214-18) concerning several _Trionyx
spinifer_ that were obtained from a commercial supply house and found to
be infested with pronocephalid trematodes (_Opisthoporus_ [=
_Teloporia_] _aspidonectes_). The closest relatives of that trematode
(also recorded from _T. ferox_) live in marine turtles. Possibly, a
Mesozoic ancestor of marine and essentially fresh-water soft-shelled
turtles harboured ancestors of these trematodes, but possibly the
parasites may have transferred relatively recently to their present
hosts. Bergounioux (1937:190) judged the Trionychidae to be an ancient
group of marine origin. Hummel (1929:770) wrote that the Trionychidae
originated in east Asia (the region of most differentiation) in humid
climates.

Baur (1891:634, 637) pointed out that the dorsal aspect of the skull of
the closely related _Carettochelys_ resembles the skull of the
Dermatemydidae, Staurotypidae and Kinosternidae; the close relationship
of _Carettochelys_ and the Dermatemydidae is also mentioned by
Bergounioux (1952:2304) and Hummel (1929:769). Hummel (_op. cit._:771)
thought that the Carettochelyidae and "die Chelydroiden" had a common
ancestor, and that (_op. cit._:772) the origin of the Trionychidae was
older than those two groups. Dunn (1931:109) wrote that the
Kinosternidae, Carettochelyidae and Dermatemydidae represented the same
general ancestry. Williams (1950:552) has shown the resemblance of the
cervical articulations in members of the Chelydridae (including
Staurotypinae and Kinosterninae) and the Central American family
Dermatemydidae. The consensus of opinion, then, is that the families
Trionychidae, Carettochelyidae, Chelydridae and Dermatemydidae are
relatively closely related.

Genus =Trionyx= Geoffroy, 1809

_Testudo_ Linnaeus (in part), Syst. Nat., Ed. 10, 1:197, 1758; type,
_Testudo graeca_ Linnaeus by subsequent designation (Fitzinger,
1843:29).

_Trionyx_ Geoffroy, Ann. Mus. Hist. Nat. Paris, 14:1, August, 1809;
type, _Trionyx aegyptiacus_ (= _Testudo triunguis_ Forskål) by
original designation.

_Apalone_ Rafinesque, Atlan. Jour., Friend of Knowledge,
Philadelphia, 1 (No. 2, Art. 12):64, Summer, 1832; type, _Apalone
hudsonica_ (= _Trionyx spiniferus_ Lesueur) by monotypy.

_Mesodeca_ Rafinesque, Atlan. Jour., Friend of Knowledge,
Philadelphia, 1 (No. 2, Art. 12):64, Summer, 1832; type _Mesodeca
bartrami_ (= _Testudo ferox_ Schneider) by monotypy.

_Aspidonectes_ Wagler, Naturl. Syst. Amphib., p. 134, 1830; type,
_Aspidonectes aegyptiacus_ Wagler (= _Testudo triunguis_ Forskål)
by subsequent designation (Fitzinger, 1843:30).

_Amyda_ Fitzinger, Ann. Wiener Mus. Naturg., 1:110, 120, 127, 1835;
type, _Amyda subplana_ Fitzinger by subsequent designation
(Fitzinger 1843:30).

_Gymnopus_ Duméril and Bibron, Erpét. Gén., 2:472, 1835; new
(substitute) name for _Aspidonectes_ Wagler.

_Pelodiscus_ Fitzinger, Ann. Wiener Mus. Naturg., 1:110, 120, 127,
1835; type, _Pelodiscus sinensis_ Fitzinger by subsequent
designation (Fitzinger, 1843:30).

_Platypeltis_ Fitzinger, Ann. Wiener Mus. Naturg., 1:109, 120, 127,
1835; type, _Platypeltis ferox_ by subsequent designation
(Fitzinger, 1843:30).

_Potamochelys_ Fitzinger, Syst. Rept., p. 30, 1843; type,
_Aspidonectes javanicus_ Wagler (= _Testudo cartilaginea_
Boddaert) by original designation.

_Tyrse_ Gray, Cat. Tort. Croc. Amphis. Brit. Mus., p. 48, 1844;
type, _Tyrse nilotica_ Gray (= _Testudo triunguis_ Forskål) by
tautonomy (_Tyrse_, a name for the Nile River).

_Callinia_ Gray, Proc. Zool. Soc. London, p. 222, 1869; new
(substitute) name for _Aspidonectes_ of Agassiz (1857:403); type,
_Callinia spicifera_ (mispelling for _spinifera_) Gray by
subsequent designation (Stejneger, 1907:514).

_Euamyda_ Stejneger, Bull. Mus. Comp. Zool., 94:7, 9, 12, 1944; new
(substitute) name for _Amyda mutica_ of Agassiz (1857:399); type,
_Amyda mutica_ Agassiz by monotypy.

_Type Species._--_Trionyx aegyptiacus_ (= _Testudo triunguis_
Forskål).

_Diagnosis._--Cutaneous femoral valves absent; width of postorbital
arch of skull less than diameter of orbit; pterygoids usually not
contacting opisthotics; carapace lacking prenuchal bone and marginal
ossifications; nuchal bone lacking conspicuous ventral ridges;
posterior margin of nuchal overlying first pair of pleurals; lateral
parts of nuchal bone overlying second pair of ribs; neurals seven or
eight, rarely six or nine; pleurals seven or eight pairs, posterior
one or two pairs sometimes in contact medially; distinct suture
usually present between hyoplastra and hypoplastra; most laterad prong
of posteromedial process of hypoplastra inserted between bifid
anterolateral process of xiphiplastra.

_Synonomy._--Geoffroy published a synopsis of the species he
recognized (1809) prior to his formal description of the genus
_Trionyx_ (1809a). Schweigger, nevertheless, probably was the first
person to recognize the soft-shelled turtles as a distinct group, and
he proposed for it the name _Amyda_ in an unpublished manuscript that
he sent to Geoffroy. The latter author (1809a:15) relegated the name
_Amyda_ to the synonomy of _Trionyx javanicus_ by means of the
following entry: "_Amyda javanica._ Schweigger, dans un manuscript
communique a l'Institut." Stejneger (1944:7) maintained that this
publication of Schweigger's monotypic generic name clearly established
its availability for the species congeneric with _Amyda javanica_ (=
_Testudo cartilaginea_ Boddaert, 1770). Loveridge and Williams
(1957:422) contend that this mere mention of the name _Amyda_ neither
constitutes the proposal of a new name nor validates it, and that the
first valid usage of the name _Amyda_ is that of Fitzinger (1835:120),
who later (1843:30) designated the type species as _Amyda subplana_.
The name _Amyda_ cannot date from _Oken_ (1816:348) as Volume 3
[Zoologie] of his Lehrbuch der Naturgeschichte published in 1815-1816
has been placed on the Official Index of Rejected and Invalid Works in
Zoological Nomenclature with the Title No. 33; see Opinion 417
(Hemming, 1956).

There has been considerable debate as to whether Geoffroy did or did
not designate a type species of the genus _Trionyx_ (1809a). Although
not specifically designated as the type species, _Trionyx aegyptiacus_
(= _Testudo triunguis_ Forskål) is considered by Smith (1930:2),
Schmidt (1953:108, footnote), and Loveridge and Williams (1957:422) to
have been sufficiently indicated by Geoffroy as the type species. But
Stejneger (1944:6), H. M. Smith (1947:122), Conant and Goin
(1948:11), and Mertens and Wermuth (1955) maintained that Geoffroy did
not adequately designate a type species, and that Fitzinger (1843:30)
designated the type species as _Trionyx granosus_ (= _Lissemys
punctata_), a synonym of Geoffroy's species, _coromandelicus_.

If Fitzinger's designation of a type species is accepted, the name
_Trionyx_ is applicable to the forms herein referred to _Lissemys_,
and _Amyda_ to the American forms. If Geoffroy's designation is
accepted, the American forms are referable to _Trionyx_, and _Amyda_
is a synonym.

The preceding includes only those generic names (listed in
chronological order) that have been applied to Recent American
soft-shelled turtles. Generic synonyms of the genus _Trionyx_
applicable to Old World species are listed by Stejneger (1907:514),
Smith (1931:165), and Loveridge and Williams (1957:420-21).

_Trionyx_ is the most widespread genus of the family; most of the
species occur in southeastern Asia. All North American soft-shelled
turtles belong to this genus.

For quick reference, all the specific and subspecific names proposed
for soft-shelled turtles in North America are listed below in
alphabetical order (left hand column) with their nomenclatural status
as recognized in this paper. The synonyms are listed in the account of
the appropriate species or subspecies, and are discussed under the
subsection entitled "Remarks."

_agassizi_ _Trionyx spinifer asper_
_annulifer_ _Trionyx spinifer spinifer_
_argus_ _Trionyx spinifer spinifer_
_asper_ _Trionyx spinifer asper_
_ater_ _Trionyx ater_
_bartrami_ _Trionyx ferox_
_emoryi_ _Trionyx spinifer emoryi_
_calvatus_ _Trionyx muticus calvatus_
_ferox_ _Trionyx ferox_
_georgianus_ _Trionyx ferox_
_georgicus_ _Trionyx ferox_
_harlani_ _Trionyx ferox_
_hartwegi_ _Trionyx spinifer hartwegi_
_hudsonica_ _Trionyx spinifer spinifer_
_mollis_ _Trionyx ferox_
_microcephalus_ _Trionyx muticus muticus_
_muticus_ _Trionyx muticus muticus_
_nuchalis_ _Trionyx spinifer spinifer_
_ocellatus_ _Trionyx spinifer spinifer_
_olivaceus_ _Trionyx spinifer spinifer_
_spiniferus_ _Trionyx spinifer spinifer_

Variation

Aside from qualitative variations and comparisons of patterns of
pigmentation the following external measurements (to the nearest
millimeter) were used.

_Length of plastron_: Maximal straight-line measurement
(midventrally), from the anteriormost region of the ventral surface to
the posterior end of the plastron; this measurement includes an
anterior cartilaginous part.

_Length of carapace_: Maximal, straight-line measurement
(middorsally), from the nuchal region to the posteriormost region of
the free edge of the carapace.

_Width of carapace_: Maximal, straight-line measurement between the
lateral margins of the carapace.

_Plane of greatest width of carapace_: Maximal, straight-line
measurement from the posteriormost region of the free edge of the
carapace to a point on the middorsal line at the level or plane of the
greatest width of the carapace; this measurement and the last two, of
course, include the fringing cartilaginous parts of the dorsal bony
carapace.

_Width of head_: Maximal measurement between the lateral margins of
the head.

_Length of snout_: Measurement from tip of snout to interorbital
region of least breadth.

_Diameter of ocellus_: Maximal outside diameter of largest (not
conspicuously ovoid or oblong) ocellus on carapace.

The following ratios were developed from the measurements. Reference
to these ratios will be made by the abbreviations within the
parentheses: length of carapace/length of plastron (CL/PL); length of
carapace/width of carapace (CL/CW); length of carapace/plane of width
of carapace (CL/PCW); length of plastron/width of head (PL/HW); width
of head/length of snout (HW/SL); diameter of ocellus/length of
plastron (OD/PL).

Secondary Sexual Variation

_Size_

In many species of turtles, females are larger than males; the
difference in size between the sexes is probably most pronounced in
aquatic emydids. The ten largest individuals of each sex were selected
to indicate the relative difference in size between the sexes of the
three American species of _Trionyx_ (excluding _ater_, Table 2).
Female soft-shelled turtles attain a larger size than males. _T.
ferox_ is the largest species; _muticus_ is the smallest. The
approximate maximal size of each sex and the difference in size
between the sexes are more correctly expressed for _spinifer_ and
_muticus_ than for _ferox_, because fewer specimens of _ferox_ were
examined; presumably the approximate maximal size of males and females
of _ferox_ is larger than is indicated in Table 2.

TABLE 2. Secondary Sexual Difference in Maximal Size of North
American Species of the Genus Trionyx (excluding ater) Based
on the Ten Largest Specimens of Each Sex of Each Species.
The Extremes Precede the Mean (in parentheses).

_Pattern_

Secondary sexual differences in pattern are probably more pronounced
in soft-shelled turtles than in other species of turtles, except
perhaps for the well-known melanism and concomitant obliteration of
pattern acquired by some adult males of the _scripta_ section of the
genus _Pseudemys_.

The difference in pattern between the sexes of American species varies
with size of the individual and with the species and subspecies. The
juvenal pattern of some individuals of _T. spinifer asper_ differs
according to sex. In the other species and subspecies, there are no
secondary sexual differences in the juvenal pattern. That pattern in
females of all species and subspecies is partly or entirely obscured
by a mottled and blotched pattern as growth proceeds. This mottled and
blotched pattern is present on females not yet sexually mature, and is
of contrasting lichenlike figures, and in other individuals is less
contrasting and a more uniform coloration. The largest males of _T.
spinifer_ retain a conspicuous juvenal pattern; in those of _muticus_
the pattern may be well-defined or partly modified and obscured,
whereas in large males of _ferox_ the juvenal pattern is ill-defined
or absent. No male normally acquires a contrasting mottled and
blotched pattern on the carapace. The pattern on the carapace of many
large individuals of _ferox_ is not distinctive as to sex.

On the dorsal surface of the soft parts of the body there is a
contrasting pattern in adult males and hatchlings of some forms, but
in most large females the pattern is usually reduced to a near-uniform
coloration; the pattern on adult males of _ferox_ and _muticus_ is not
contrasting and resembles that on large females.

_Coloration_

Because most specimens examined were preserved, the detection of
secondary sexual differences in coloration was difficult. There is one
difference in coloration between the sexes in the subspecies _T. s.
emoryi_. Males from the Río Grande drainage, at least those from the
Big Bend region of Texas, and southwestward in the Río Conchos into
Chihuahua, México, are bright orange on the side of head (postlabial
and postocular pale areas); an orange tinge also occurs in pale
stripes on the snout, and pale orange blotches sometimes occur on the
dorsal surfaces of limbs, especially the hind limbs. The coloration of
these areas on females is pale yellow, lacking orange.

_Tuberculation_

In all subspecies of _spinifer_ the carapace of adult males is
"sandpapery" owing to abundant, small, spiny tubercles distributed
over its surface; all females lack spiny tubercles on the surface of
the carapace.

_Length of Tail_

Elongation of the preanal region of the tail resulting in the
extension of the cloacal opening beyond the posterior edge of the
carapace occurs in males of several kinds of turtles, including
_Trionyx_, at least in those from Louisiana, Texas, and Lake Texoma,
Oklahoma (Webb, 1956:121). Probably this elongation is characteristic
of males of all American softshells. Some females of _spinifer_ and
_muticus_ that exceed the maximum size attained by males have the tip
of the tail and cloacal opening extending a short distance beyond the
posterior edge of the carapace. Some large females of _ferox_ have
more elongate tails than those of _spinifer_ and _muticus_.

_Width of Alveolar Surfaces of Jaws_

Stejneger (1944:34-36, pl. 6) commented on a series of large skulls of
_ferox_ mostly from Kissimmee, Florida, some of which had
conspicuously expanded alveolar surfaces. He suggested that the
condition was confined to large males. A scattergram (Fig. 2) based on
measurements obtained from 45 skulls of _ferox_ shows widened alveolar
surfaces of the upper jaws on some of the larger skulls. Because the
maximal size of adult males is unknown and the difference in size
between the sexes of _ferox_ is slight, such large skulls might
represent either sex. The sex had been recorded for only three of the
45 skulls; none of the three exceeded 82 millimeters in basicranial
length or had widened alveolar surfaces. Some of the larger skulls of
approximately the same size differ markedly in width of the alveolar
surfaces; this difference suggests that both sexes are included and
that the sexes may be of approximately the same maximal size. On the
other hand, the variation observed in skulls is possibly confined to
one sex. To judge from what is known of the maximal sizes of the sexes
of _spinifer_ and _muticus_ (see Table 2), skulls of _ferox_ of more
than 85 millimeters in basicranial length probably are of females. The
largest alcoholic male (dissected) of _ferox_ that I examined had a
width of head of approximately 46.5 millimeters; that measurement
corresponds to a basicranial length of 70 to 75 millimeters. The
specimen of which measurements are depicted by the uppermost symbol in
the scattergram (represented by KU 16528) was recorded as a female.
Large females of _T. s. asper_ from rivers emptying into the Atlantic
Ocean have broadened alveolar surfaces.

[Illustration: FIG. 2. Basicranial length and greatest width of
alveolar surface of upper jaw on 45 skulls of _T. ferox_. Some
skulls (sex unknown) in which the basicranial length exceeds
85 mm. develop widened alveolar surfaces of the jaws.]

_Length of Claw_

Secondary sexual differences in length of claw on the forelimb are
pronounced in some kinds of turtles. Cahn (1937:178) stated that the
female of _Trionyx muticus_ usually has long claws on the hind feet,
while the male has long claws on the forefeet, but I am unable to
substantiate his statement. Measurements of length of the third claw
on the hind limb taken in 41 males and 45 females of _spinifer_ from
Louisiana showed no secondary sexual difference.

Ontogenetic Variation

_Pattern_

In all species and subspecies the juvenal pattern is replaced in
females as growth proceeds by a mottled and blotched pattern that is
contrasting or of nearly uniform coloration. The blotched pattern (of
lichenlike figures) is evident on the carapaces of most females that
have plastra so long as 8.0 centimeters. The contrasting juvenal
pattern on the dorsal surfaces of the soft parts of the body is
correspondingly modified in females, but at a size larger than 8.0
centimeters. Size of ocelli (OD/PL) in _T. s. spinifer_ and _hartwegi_
seems to vary ontogenetically (see section on Geographic Variation).

Some hatchlings have blotched patterns (_T. spinifer asper_, TU
16689.2, plastral length, 3.5 cm.); the largest females examined that
did not show any evidence of mottling were two _asper_ having
plastrons 7.6 and 8.0 centimeters in length. Variation in color and
pattern probably is modified greatly by the environment (Heude _in_
Stejneger, 1907:518, footnote d) and the physiological condition of
the individual. Smith, Nixon and Minton (1949:92) reported that a
female of _T. s. hartwegi_ developed a striking melanistic pattern in
captivity and they concluded that patterns of soft-shelled turtles may
be produced not only by conventional chromatophores, but also by other
depositions, both intra- and extracellular. TU 16170, taken from
brackish water at Delacroix Island, St. Bernard Parish, Louisiana, is
the only adult male I have seen that had a blotched pattern
(orange-brown in life) on the carapace in addition to the juvenal
pattern. One female of _muticus_, KU 48229, having a plastral length
14.5 centimeters, retained a well-defined juvenal pattern, and lacked
a mottled and blotched pattern (see Pl. 46).

_Tuberculation_

Males of the subspecies of _spinifer_ develop small, sharp tubercles
on the dorsal surface of the carapace when sexually mature. As growth
proceeds, the minute prominences along the anterior edge of the
carapace on hatchlings of both sexes of _spinifer_ change in shape to
conical projections or low, flattened, scarcely-elevated prominences,
depending on the subspecies (Fig. 8).

Large females of _spinifer_ and _ferox_ acquire enlarged, flattened
knobs in the nuchal region and posteriorly in the center of the
carapace.

_Length of Tail_

The preanal region of the tail rapidly elongates in males of all
soft-shells when they are sexually mature.

_Width of Alveolar Surfaces of Jaws_

The alveolar surfaces of the jaws are conspicuously broadened in large
adults of _ferox_, and females of that population of _T. s. asper_ in
the Atlantic Coast drainage.

_Ratios_

Width of head increases at a rate slightly slower than does the length
of the plastron (PL/HW, Fig. 3). The change in proportions is most
pronounced at a plastral length of 7.5 to 8.0 centimeters. In
general, the head is narrowest in _muticus_ and widest in _ferox_. _T.
s. asper_ and _emoryi_ seemingly have the widest heads among the
subspecies of _spinifer_. Geographically width of head increases from
_spinifer_ and _hartwegi_ through _pallidus_ and _guadalupensis_ to
_emoryi_. _T. ater_ terminates the cline; 12 specimens, ranging in
plastral length from 9.6 to 18.4 centimeters, resemble _ferox_ and
_asper_ in having wide heads (average PL/HW of 4.93).

[Illustration: FIG. 3. Ratio of length of plastron to width of head
(PL/HW) in some American species and subspecies of the genus
_Trionyx_. The size of each sample is given in parentheses
following an indication of the range (< = less than, > = greater
than) in length of plastron (in cm.) of each sample. The horizontal
line indicates the observed variation; the vertical line, the mean;
the white rectangle, four standard deviations; and the black
rectangle, four standard errors of the mean. There is some
ontogenetic variation in PL/HW. The head is narrowest in _muticus_
and widest in _ferox_.]

The carapace increases in width more slowly than it increases in
length (CL/CW, Fig. 4). The change in proportions is most pronounced
when the carapace is 8.0 to 8.5 centimeters in length. Ontogenetically
_muticus_ varies least and _ferox_ most; large specimens of _ferox_
have narrower carapaces than _muticus_ of corresponding size. There is
also an indication of a geographical gradient that parallels the cline
mentioned above for PL/HW. There is a gradual decrease in width of
carapace from _pallidus_ through _guadalupensis_ to _emoryi_. Of the
subspecies of _spinifer_, _emoryi_ has the narrowest carapace and
resembles _ferox_. In _T. ater_ this cline is accentuated and
terminates; 12 specimens, ranging in plastral length from 9.6 to 18.4
centimeters, resemble _ferox_ and _emoryi_ in having narrow carapaces
(average CL/CW of 1.32).

_Osteological Characters_

Closure of the anterior, paravertebral fontanelles on the bony
carapace, and size and number of plastral callosities are subject to
ontogenetic variation (see sections entitled "Carapace" and
"Plastron").

[Illustration: FIG. 4. Ratio of length of carapace to width of
carapace (CL/CW) in some American species and subspecies of the
genus _Trionyx_. Symbols as in Fig. 3. There is some ontogenetic
variation in CL/CW (least in _muticus_). The carapace is
narrowest in _ferox_ and _emoryi_, and widest in _muticus_,
_pallidus_ and _asper_.]

[Illustration: FIG. 5. Pattern on dorsal surface of snout of some
American species and subspecies of the genus _Trionyx_. Note the
gradual transition in pattern from that of _hartwegi_ (b) and
_asper_ (c) to that of _emoryi_ (h).

a. _T. ferox_ (UMMZ 102276, × 1/3)
b. _T. spinifer hartwegi_ (KU 46742, × 3/4)
c. _T. spinifer asper_ (KU 50842, × 1)
d. _T. spinifer pallidus_ (KU 2958, × 1/2)
e. _T. spinifer pallidus_ (KU 2934, × 1/2)
f. _T. spinifer pallidus_ (KU 2947, × 1/2)
g. _T. spinifer guadalupensis_ (TU 10165, × 2/3)
h. _T. spinifer emoryi_ (KU 48218, × 2/3)
i. _T. muticus muticus_ (KU 48236, × 2/3)
]

Geographic Variation

Geographic variation occurs in _Trionyx spinifer_ and _T. muticus_.
The variant populations of _spinifer_ are segregated into six
subspecies, those of _muticus_ into two. In the subspecies of
_spinifer_ there is both group variation and clinal variation.

Group Variation

The six subspecies of _spinifer_ can be separated into two groups on
the basis of the juvenal pattern. One group (subspecies _spinifer_,
_hartwegi_ and _asper_) has a pattern of dark spots or ocelli of
various sizes on the carapace, whereas the other group (subspecies
_pallidus_, _guadalupensis_ and _emoryi_) has a pattern of small white
dots or tubercles on the carapace. The two groups differ also in the
manner in which the mottled and blotched pattern first appears on the
carapace of females. Usually, contrasting lichenlike figures initially
surround the dark spots or ocelli on the carapace in females of the
_spinifer_ group (less evident in _pallidus_), whereas females of the
_emoryi_ group usually lack a contrasting pattern early in ontogeny.
In general, the two groups differ in the degree of pigmentation. The
_spinifer_ group has larger marks and more contrasting patterns on the
head and limbs, and more extensive pigmentation on the ventral surface
than members of the _emoryi_ group. _T. ater_ is more closely related
to those subspecies of the _emoryi_ group but differs in having the
ventral surface heavily speckled with black and an over-all blackish,
dorsal coloration; the underlying pattern of _ater_ resembles that of
_emoryi_.

Clinal Variation

Several characters are arranged in a geographical gradient or cline.
Some characters are relatively uniform and represent a terminus in the
_spinifer_ group. Some characters change gradually and successively
through the subspecies _pallidus_ and _guadalupensis_, and terminate
in _emoryi_ and _T. ater_. Some characters of _ater_, in turn, show
affinity with _T. muticus_ and _T. ferox_.

_Pattern on Snout_

The pattern (Fig. 5) on the snout usually consists of pale,
dark-bordered stripes that form an acute angle in front of the eyes in
_spinifer_, _hartwegi_ and _asper_, but the corresponding marks form a
dark triangle the base line of which joins the anterior margins of the
orbits in _emoryi_ and usually in _guadalupensis_. In _pallidus_, the
geographic range of which is between _guadalupensis_ and _hartwegi_,
there are different patterns that are in various degrees intermediate
between those described immediately above for _hartwegi_ and
_guadalupensis_.

_Pattern on Side of Head_

The change in pattern (Fig. 6) and its contrast with the ground color
on the side of the head parallels the sequence of changes in pattern
on the snout. The pattern on the side of head contrasts with the
ground color and consists of dark markings below the eye and on the
neck, an indication of a postlabial stripe, and a pale, dark-bordered
postocular stripe that may be variously interrupted (_spinifer_ and
_hartwegi_; _asper_ usually has uninterrupted postocular and
postlabial stripes that unite on the side of the head). The pattern is
contrasting but variable in _pallidus_. _T. s. emoryi_ and usually
_guadalupensis_ have fewer dark markings, sometimes none, and an
interrupted postocular pale stripe that produces a pale blotch just
behind the eye.

[Illustration: FIG. 6. Pattern on side of head of some American
species and subspecies of the genus _Trionyx_. Note the gradual
reduction in contrast of pattern and interruption of the postocular
stripe from that of _spinifer_ (b) to that of _emoryi_ (f).

a. _T. ferox_ (UMMZ 102276, × 1/3)
b. _T. spinifer spinifer_ (UMMZ 54401, × 2/3)
c. _T. spinifer asper_ (KU 50843, × 2/3)
d. _T. spinifer pallidus_ (KU 50830, × 3/4)
e. _T. spinifer guadalupensis_ (SM 659, × 2/3)
f. _T. spinifer emoryi_ (KU 2922, × 3/4)
g. _T. muticus muticus_ (KU 48228, × 2/3)
h. _T. muticus calvatus_ (KU 47117, × 2/3)
]

[Illustration: FIG. 7. Pattern on the dorsal surface of the distal
part of the right hind limb of some American species and subspecies
of the genus _Trionyx_. Note the gradual reduction in contrast of
pattern from that of _hartwegi_ (a) to that of _emoryi_ (d).

a. _T. spinifer hartwegi_ (KU 15932, × 3/4)
b. _T. spinifer pallidus_ (KU 40175, × 2/3)
c. _T. spinifer guadalupensis_ (TU 10165, × 3/4)
d. _T. spinifer emoryi_ (KU 3153, × 5/6)
e. _T. muticus muticus_ (KU 48228, × 3/4)
f. _T. ferox_ (UMMZ 102276, × 1/2)
]

[Illustration: FIG. 8. Shape of tubercles on anterior edge of
carapace in some American species and subspecies of the genus
_Trionyx_ (× 1/2). Note the gradual reduction in size of
tubercles from that of _hartwegi_ (b) to that of _muticus_ (h).

a. _T. ferox_ (UMMZ 90010)
b. _T. spinifer hartwegi_ (KU 3346)
c. _T. spinifer pallidus_ (TU 13213)
d. _T. spinifer guadalupensis_ (TU 10160)
e. _T. spinifer emoryi_ (KU 2906)
f. _T. ater_ (KU 46906)
g. _T. muticus muticus_ (KU 48229)
h. _T. muticus muticus_ (KU 48232)
]

_Pattern on Dorsal Surface of Limbs_

A corresponding sequence of change occurs in the size of dark markings
on the dorsal surface of the limbs (Fig. 7). The hind limb usually has
larger markings than the forelimb. The change is gradual from larger
and darker markings (contrasting pattern) in _hartwegi_, _spinifer_
and _asper_ to smaller and paler markings (non-contrasting pattern) in
_emoryi_.

_Tuberculation_

There is also a cline in tuberculation (Fig. 8) that parallels
geographically the sequence of changes in patterns mentioned
immediately above. The size of the tubercles along the anterior edge
of the carapace changes in both sexes from those that are enlarged and
equilateral or conical in shape in _spinifer_, _hartwegi_, _asper_ and
_pallidus_ to those that are scarcely elevated in _guadalupensis_,
_emoryi_ and _T. ater_. Indeed, in the three kinds mentioned last, the
tubercles are absent in some specimens. There seems to be a
corresponding reduction in the size and number of small, sharp-tipped
tubercles that cover the carapace in adult males; the carapace of _T.
ater_ is mostly smooth and has only a few small, whitish tubercles.

[Illustration: FIG. 9. Anteroposterior position of plane of
greatest width of carapace (CL/PCW) in some American species
and subspecies of the genus _Trionyx_. Symbols as in Fig. 3.
The greatest width of carapace is midway between anterior and
posterior ends in _ferox_, _spinifer_, _hartwegi_, _asper_ and
_muticus_, and farther posterior in the other subspecies of
_spinifer_.]

_Ratios_

The clinal tendencies in PL/HW (Fig. 3) and CL/CW (Fig. 4) that
parallel those mentioned above for pattern and tuberculation have
already been mentioned under the section "Ontogenetic Variation."

The ratio of CL/PCW (Fig. 9) was used in an effort to show further
differences in the shape of the carapace, especially the plane on the
carapace where the greatest width occurs. Figure 9 shows the greatest
width to be approximately midway between the anterior and posterior
ends in the subspecies _spinifer_, _hartwegi_ and _asper_, and in the
species _ferox_ and _muticus_ (CL/PCW of 2.00). The greatest width of
carapace is more posterior and at approximately the same plane in
_pallidus_ and _guadalupensis_, and farther posterior in _emoryi_.
Calculated ratios for 12 specimens of _T. ater_ average 2.15, a value
that suggests closer affinity with _pallidus_, _guadalupensis_ and
_emoryi_ than to the other species and subspecies.

Comparison of the relative lengths of snout (HW/SL, Fig. 10) in
different populations of _T. spinifer_ shows a character gradient. To
facilitate a comparison utilizing large samples, the subspecies
_spinifer_ was combined with _hartwegi_, and _pallidus_ with
_guadalupensis_. The snout is longer in the subspecies _spinifer_ and
_hartwegi_ than in _emoryi_; the length of the snout of _emoryi_
resembles that of _T. ferox_. The snout is proportionately the longest
in _T. muticus_. The average ratio of HW/SL for 12 individuals of _T.
ater_ is 1.37, and is nearer that of _pallidus_, _guadalupensis_,
_emoryi_ and _ferox_ than that of _muticus_ or the other subspecies of
_T. spinifer_.

[Illustration: FIG. 10. Ratio of width of head to length of snout
(HW/SL) in some American species and subspecies of the genus
_Trionyx_. Symbols as in Fig. 3. Values for _spinifer_ are
combined with those of _hartwegi_, and those of _pallidus_
with _guadalupensis_. The snout is proportionately the
longest in _muticus_.]

Size of the ocelli increases from west to east in populations of _T.
spinifer_ in the upper Mississippi River and Great Lakes drainages.

The ratio of OD/PL (Fig. 11) varies considerably but gradually
increases from Kansas northeastward to Michigan. The minimal diameter
of any ocellus recorded was one millimeter; solid dots on the carapace
(_hartwegi_) were also recorded as one millimeter. Larger ratios are
usually derived from measurements of larger individuals. Seemingly,
there should be a clinal tendency in ontogenetic variation paralleling
the size of ocelli and dependent on it; ontogenetic variation should
be least in western populations in which the size of ocelli does not
change appreciably with increasing size, and should be greatest in
eastern populations in which the ocelli on adult males are larger than
those on the carapace of young turtles. It is difficult to
demonstrate ontogenetic variation because specimens of corresponding
size from the same general area may have ocelli of different sizes.
The gradient in size of ocelli is also indicated by specimens from
other states. I have the subjective impression that there is least
variation in specimens from Michigan (Great Lakes-St. Lawrence River
drainage), but this is not clearly shown by Figure 11.

[Illustration: FIG. 11. Ratio of diameter of ocellus to length of
plastron (OD/PL) in _T. spinifer_ from some states in the upper
Mississippi River and Great Lakes drainages. Symbols as in
Fig. 3. The size of the ocelli on the carapace gradually
increases from Kansas northeastward to Michigan.]

Character Analysis

_Snout_

The snout (Fig. 12) is tubate having terminal nostrils separated by a
vertical septum. One of the principal characters distinguishing _T.
ferox_ and _T. spinifer_ from _T. muticus_ is a lateral, whitish ridge
projecting from each side of the nasal septum (hereafter referred to
as septal ridges but often referred to in the literature as a
papilla). The shape of the end of the snout is truncate in _T. ferox_
and _T. spinifer_, and the nostrils are larger than in _T. muticus_.
In _muticus_ the snout usually terminates somewhat obliquely, and the
nostrils tend to be slightly inferior; also, the end of the snout is
usually rounded and somewhat pointed, causing the nostrils to be
visible in lateral view. Some _T. muticus_ do not differ markedly from
_ferox_ or _spinifer_ in shape of the end of the snout. Stejneger
(1944:14) mentioned indication of a septal ridge that did not reach
the opening of the nostril in _muticus_. I have slit the outer edge of
the nostril on several specimens of _muticus_, and have not noticed an
indication of a septal ridge.

[Illustration: FIG. 12. Shape of snout in _T. spinifer_ (left, a-d,
from KU 46907) and _T. muticus_ (right, e-h, from KU 48236).
Lateral views--a, e (× 1); anterior views--b, f (× 5); dorsal
views--c, g (× 2.5); ventral views--d, h (× 2.5).]

_Tuberculation_

Tubercles or obtuse prominences occur on the anterior edge of the
carapace (Fig. 8) or on the dorsal surface of the carapace. _Trionyx
muticus_ lacks tubercles, although some individuals show shallow,
widely spaced wrinkles that suggest prominences on the anterior edge
of the carapace. Both sexes of _T. ferox_ have prominences, resembling
flattened hemispheres, on the anterior edge of the carapace and in the
nuchal region. Large females of _ferox_ have obtuse prominences in the
center of the carapace posteriorly, some of which are often arranged
in longitudinal rows. The surface of the carapace in both sexes of _T.
ferox_ has small closely-set, blunt tubercles arranged in rows that
resemble longitudinal ridges (most evident in juveniles).

Large females of _T. spinifer_ have obtuse prominences in the center
of the carapace posteriorly, some of which in many specimens are
arranged in longitudinal rows; I cannot discern any correlation of
number or arrangement of prominences with size in _spinifer_ or
_ferox_. The carapace in adult males of _spinifer_ bears small, sharp
tubercles that make the surface feel like sandpaper. The tubercles on
the anterior edge of the carapace in adults of both sexes vary from
round to equilateral and conical to low and flattened (see comments on
tuberculation under subsection entitled "Geographic Variation"). Some
large females of the same subspecies have tubercles on the anterior
edge of the carapace that may be conical (higher than wide) or
equilateral. The difference in shape of the tubercles seems not to be
correlated with size because one _T. s. pallidus_, 30.5 centimeters
(TU 13212) has prominent but blunted and equilateral tubercles,
whereas, another female of _pallidus_, 20.8 centimeters (TU 13210),
from the same locality has higher, conical tubercles. The blunted,
equilateral tubercles may be the result of environmental wear, or the
difference in shape of tubercles may be due to individual variation.

_Pattern on Carapace_

Two features of the pattern on the carapace are of taxonomic worth: 1)
the width and distinctness of the pale rim at the periphery of the
carapace (marginal rim), if present, and 2) the kind of pattern on the
carapace (juvenal pattern). The marginal rim is absent in females of
_T. ater_, and only faintly evident in males. The marginal rim is
obscured or absent (adult males and females) and is not separated from
the ground color of the carapace by a dark marginal line in hatchlings
of _T. ferox_. The carapace of _T. muticus_ has a marginal rim that is
usually separated from the ground color of the carapace by an
ill-defined, dark marginal line; some individuals lack the marginal
dark line. The subspecies of _T. spinifer_ have a well-defined, dark,
marginal line that separates the marginal rim from the ground color of
the carapace; _T. s. asper_ has more than one dark marginal line on
the carapace. The marginal rim is ill-defined and blotched, or absent,
in large females of all species of _Trionyx_.

The marginal rim is widest at the posterior end of the carapace and
lacking in the nuchal area. The width of the pale marginal rim is very
narrow, almost to the degree of being absent, in juveniles of _T.
ferox_. _T. s. emoryi_ has a pale, marginal rim that is four or five
times wider posteriorly than it is laterally, whereas posteriorly the
width of the rim in the other subspecies of _T. spinifer_ and in the
species _T. muticus_ is only two or three times wider posteriorly than
it is laterally.

The juvenal pattern commonly consists of whitish tubercles or dots
(_T. s. emoryi_, _T. s. guadalupensis_, _T. s. pallidus_, _T. ater_),
large black ocelli (_T. s. spinifer_), small black dots and ocelli
(_T. s. hartwegi_, _T. s. asper_), large dusky spots or ocelli (_T. m.
calvatus_), or small dusky dots or short streaks and dashes (_T. m.
muticus_). Some hatchlings of _pallidus_ and _emoryi_ have a uniform
pale brown or tan carapace; hatchlings of _T. ferox_ have a
distinctive pattern (Pl. 31). Further comments and illustrations
pertaining to kind of pattern on the carapace are offered under the
accounts of species and subspecies.

_Pattern on Dorsal Surface of Snout (Fig. 5)_

_T. ferox_ has pale stripes on a dark background that unite in front
of the eyes; the dark ground color becomes paler with increasing size,
but the stripes retain thick black borders. _T. m. muticus_ has
ill-defined, pale stripes that are evident just in front of the eyes
and do not extend anteriorly to unite in front of the eyes, whereas
_T. m. calvatus_ lacks pale stripes on the snout. The kind of pattern
on the dorsal surface of the snout that is characteristic for each of
the subspecies of _T. spinifer_ has been mentioned in the discussion
of clinal variation.

_Pattern on Side of Head (Fig. 6)_

_T. ferox_ has a pale broad, postocular stripe in contact with the
orbit or not, and other pale marks on a dark background; the ground
color becomes paler with increasing size, but the stripes and other
marks retain thick black borders. _T. m. muticus_ usually has an
uninterrupted, dusky-bordered, postocular stripe, whereas _T. m.
calvatus_ (in adult males only) has pale postocular stripes with thick
blackish borders. The pattern on the side of head that is
characteristic for each subspecies of _T. spinifer_ has been mentioned
in the discussion of clinal variation.

_Pattern on Dorsal Surface of Limbs (Fig. 7)_

Young specimens of _T. ferox_ have pale marks on a blackish
background. As growth proceeds the distinctive contrasting pattern is
obliterated and eventually is replaced by a uniform grayish coloration
in large adults. The pattern on the limbs of _T. muticus_ is not
contrasting, and is almost a uniform grayish, consisting of fine, pale
markings. The clinal variation in pattern and kind of pattern on the
limbs of the subspecies of _T. spinifer_ has been mentioned in the
discussion of clinal variation. Dark markings tend to form streaks
that are coincident with the digits, and larger markings occur on the
hind limbs than on the forelimbs.

_Marginal Ridge_

The anterolateral edge of the carapace in _T. ferox_ (both sexes and
all sizes) is "folded over" into a ridge having a distinct inner
margin (Pls. 1 and 2), which is hereafter referred to as the marginal
ridge. Siebenrock (1924:184-85) referred to this ridge as a
"Hautsäume" and mentioned its occurrence in Old World species of the
genus _Trionyx_. The marginal ridge is not present in _T. muticus_,
_T. spinifer_ or _T. ater_.

_Ratios_

The means of some samples (Fig. 3) differ in regard to PL/HW, but the
ranges of variation overlap so much that little significance can be
attributed to the difference. _T. ferox_, and to a lesser extent _T.
s. emoryi_ and _T. s. asper_, have slightly larger heads than the
other forms. The width of head is proportionately the smallest in _T.
muticus_; in most individuals of it having a plastron so long as 13.0
centimeters, the width of the head is less than 16 per cent of the
length of the plastron--a percentage that is distinctive.

The visibly narrower carapace (CL/CW, Fig. 4), suggesting an ovoid or
oblong shape, in some large individuals of _T. ferox_ and _T. s.
emoryi_ is indicated by the large ratio in specimens that have a
plastral length of 8.0 centimeters or more. Nevertheless, the degree
of overlap of the ranges of variation is such that this ratio is of
relatively little use taxonomically.

The greatest width of the carapace is farther posterior in _T. s.
emoryi_ than in the other forms (CL/PCW, Fig. 9). The considerable
overlap of the range of variation of this ratio for _emoryi_ with the
other forms limits its usefulness as a taxonomic character.

The snout is proportionately shortest in _ferox_ and _T. s. emoryi_,
and longest in _muticus_ (HW/SL, Fig. 10). The most marked difference
in this ratio is between the species _muticus_ and _ferox_; the ranges
of variation of those species overlap to a degree that tends to negate
the taxonomic usefulness of this character.

Most adults and subadults of _T. ferox_ show clearly in dorsal view
the anterolateral portions of the plastron. This condition is much
less well developed in some specimens of _T. s. emoryi_. _T. ferox_ is
extreme in the ratio CL/PL (relatively the longest plastron or
shortest carapace, Fig. 13). _T. s. asper_ has the shortest plastron
in relation to length of carapace. Calculated ratios for 12 _T. ater_
average 1.36, a value that suggests close affinity with some
subspecies of _T. spinifer_ (_pallidus_, _guadalupensis_, _emoryi_).
Because of the degree of overlap of the ranges of variation in all
forms, little significance can be attributed to the difference in
means of _ferox_ and _asper_.

[Illustration: FIG. 13. Ratio of length of carapace to length of
plastron (CL/PL) in some American species and subspecies of
the genus _Trionyx_. Symbols as in Fig. 3. _T. ferox_ has
proportionately the shortest carapace.]

_Scalation_

Cornified, smooth or cusplike areas occur on each limb, but their
number and arrangement are of no taxonomic value. Normally, the
anterior surface of each forelimb possesses four cornified areas for
which the term antebrachial scales is proposed (Fig. 14). Two of the
four scales occur in a more dorsal position; the lateral edge of the
proximal one is free and cusplike along a part of its length, whereas
the distal scale is smooth-edged. Two scales having their lateral
edges free and cusplike are ventral in position, and closer together
than the two dorsad scales. Size of the scales and length of the free
cusplike edges vary. Occasionally adjacent scales are fused or small
additional scales are present. The number, configuration and
arrangement of the two cornified areas on each hind limb are constant.
One of these scales is smooth-edged and occurs posteriorly on the
dorsal surface. The other scale, situated on the ventral surface
posteriorly in the region of the heel and distal to the smooth-edged
scale of the dorsal surface, has a pronounced, cusplike, free edge.

[Illustration: FIG. 14. Dorsal surface of right forelimb showing
normal number and arrangement of antebrachial scales in American
species of the genus _Trionyx_ (_T. spinifer hartwegi_,
KU 15932, × 3/4).]

_Choanal Papillae_

This term refers to the papillate flaps of skin that project from the
lateral borders of the internal nares. Webb and Legler (1960:23) noted
their presence in softshells, and Parsons (1958) discussed their
occurrence in sea turtles of the family Cheloniidae and in the
testudinid subfamily Emydinae (1960). In preserved softshells the
choanal papillae may extend laterally and partly cover the nares, or
may be folded vertically against the lateral borders of the nares; in
the latter position the papillae are easily overlooked. To my
knowledge, choanal papillae occur in all American species and
subspecies of soft-shelled turtles. The free edge of each narial flap
shows various degrees of fimbriation. The fimbriated border is least
developed (margin nearly entire) in _T. muticus_ and most developed in
_T. ater_ and _T. ferox_. In _ater_ at least, the anteriormost
portions of the narial flaps seem wider than in the other forms and
show a greater degree of fimbriation than the posteriormost parts. The
choanal papillae are most easily observed in large specimens.

_Skull_

In general, there is less difference between the skulls of _ferox_ and
_spinifer_ than between either of those species and _muticus_
(Stejneger, 1944:10-11). Figure 15 shows the general differences in
proportions of the skulls of _spinifer_ and _muticus_; Plate 54 shows
the skull of the holotype of _Platypeltis agassizi_ (= _T. s. asper_),
which is similar to that of _ferox_; Stejneger (_op. cit._) provided
labelled drawings of the skull of _T. spinifer_ as well as photographs
of skulls of other forms.

The total of 159 skulls examined by me include 80 of _spinifer_, 50 of
_ferox_, and 29 of _muticus_. There are no secondary sexual
differences between skulls of corresponding size, except in
_agassizi_-form skulls mentioned under the account of _T. s. asper_,
and possibly in _ferox_. Most, and possibly all, of the skulls of
_muticus_ having a basicranial length of 40.0 millimeters or more, and
those of _spinifer_ exceeding 50.0 millimeters must represent females
(by correlation of known maximum size of males with greatest width of
head, which is, in turn, compared with the greatest width of skull and
corresponding basicranial length).

[Illustration: FIG. 15. Skulls of _Trionyx spinifer hartwegi_ (left,
a-d, KU 2757), and _Trionyx muticus muticus_ (right, e-h, KU 1870).
Dorsal views, a (× 1/2), e (× 3/4); occipital views, b (× 5/6),
f (× 1); lateral views, c (× 1/2), g (× 3/4); ventral views,
d (× 1/2), h (× 3/4).

a., alveolar surface of upper jaw
aq., articular surface of quadrate
ex., exoccipital
fp., fenestra postotica
fm., foramen magnum
if., intermaxillary foramen
ic., internal choana
mx., maxilla
mxb., maxillary bridge
oc., occipital condyle
op., opisthotic
ope., opisthotic-exoccipital spur
opw., opisthotic wing
pmx., premaxillaries (fused)
pt., pterygoid
q., quadrate
qj., quadratojugal
sq., squamosal
s., supraoccipital spine
tc., tympanic cavity
]

Measurements used include basicranial length (occipital condyle to tip
of upper jaw), greatest width (variable in position), greatest width of
alveolar surface of maxilla (taken at level immediately posterior to
anterior margin of internal choanae), greatest length of internal
choanae, and least breadth of maxillary bridge (separating internal
choanae and intermaxillary foramen). One ratio developed from the
measurements was greatest length of internal choanae/least breadth of
maxillary bridge, hereafter referred to as IC/MB. This ratio is
discussed under the account of _T. s. asper_.

_Greatest Width_

The position or level on the skull where the greatest width (Table 3)
occurs is of some diagnostic value in distinguishing the skulls of
_ferox_ from _spinifer_ and _muticus_. Skulls of _ferox_ usually are
widest at the level of the quadratojugal (immediately in front of
tympanic cavity), whereas skulls of _spinifer_ and _muticus_ usually
are widest slightly more posteriorly at a level on the squamosal
immediately behind the tympanic cavity. Occasionally the width at the
level of the quadratojugal and squamosal is the same, or the greatest
width of skull may be ventrad between the quadrates, which are
slightly flared laterally. The latter condition possibly is most
prevalent in _muticus_.

TABLE 3. Variation in Position of Greatest Width of Skull of North
American Species of the Genus Trionyx (excluding ater). The Number
of Specimens Examined (in Parentheses) Follow the Specific Names.

================+=================================================
| Species
POSITION +--------------+-----------------+----------------
| _ferox_ (36) | _spinifer_ (47) | _muticus_ (14)
----------------+--------------+-----------------+----------------
Squamosal | 7 (19%) | 35 (74%) | 11 (79%)
Quadratojugal | 26 (72%) | 7 (15%) | 1 (7%)
Quadrate | 2 (6%) | | 2 (14%)
Squamosal and | | |
quadratojugal | | |
of same width | 1 (3%) | 5 (11%) |
----------------+--------------+-----------------+----------------

_Supraoccipital Spine_

The ventral surface of the supraoccipital spine in _muticus_ lacks a
medial ridge, and gradually increases in width anteriorly, so that it
is widest proximally in the region of the roof of the foramen magnum.
In _ferox_ and _spinifer_, the ventral surface, usually having a
medial ridge, is narrow and of the same width throughout its length or
somewhat flared distally. The ventral surface of the supraoccipital
spine, which is widest proximally in _muticus_, is always narrow
proximally in _ferox_ and _spinifer_. The ventral surface of the
supraoccipital spine of one skull of _spinifer_, USNM 91311, differs
little from that of _muticus_.

_Foramen Magnum_

The shape of the foramen magnum is generally rhomboidal in _spinifer_
and _ferox_; the ventral angle is semicircular, the lateral angles
obtuse, and the dorsal angle more acute. The shape of the foramen
magnum in _muticus_ is ovoid, higher than wide; the sides are evenly
rounded.

_Opisthotic-Exoccipital Spur_

Skulls of _spinifer_ normally have the fenestra postotica partly
restricted by a medially-slanting, descending spur from the roof of
the fenestra postotica; the spur incorporates the suture between the
exoccipital and opisthotic and includes parts of those two bones. On
one skull (KU 2824) the spur is displaced more medially and does not
incorporate the opisthotic. The descending spur contacts the pterygoid
ventrally forming a complete bony strut traversing the fenestra
postotica in some skulls (KU 2228, 2666, 2762, TU 15423, MCZ 46621, TU
15415, right side only). The fenestra postotica on skulls of _ferox_
and especially _muticus_ is not normally restricted by an
opisthotic-exoccipital spur.

Often the spur is reduced and indicated by a smooth projecting ridge.
Sometimes the spur or ridge is absent on skulls of _spinifer_, and I
have seen no well-developed spur on a skull of _muticus_. The
development of the spur is not due to ontogenetic variation. There is
some variation in development of the spur on either side of the skull;
two skulls of _ferox_ have the combination ridge/absent, and two of
_spinifer_ have the combinations ridge/spur and spur/absent. The
frequency (based on counts of individual skulls) and the degree of
development of the spur among the three species is indicated in Table
4.

TABLE 4. Frequency and Degree of Development of Opisthotic
Exoccipital Spur of North American Species of the Genus Trionyx
(excluding ater). The Number of Specimens Examined (in Parentheses)
Follow the Specific Names.

======================+=================================================
| Species
DEVELOPMENT OF SPUR +--------------+-----------------+----------------
| _ferox_ (43) | _spinifer_ (68) | _muticus_ (29)
----------------------+--------------+-----------------+----------------
spur (well-developed) | 1 (2%) | 45 (66%) |
ridge (reduced) | 7 (16%) | 20 (30%) | 1 (3%)
absent | 35 (82%) | 3 (4%) | 28 (97%)
----------------------+--------------+-----------------+----------------

Loveridge and Williams (1957:415, footnote) cited Siebenrock who
mentioned a descending process of the opisthotic in _Dogania_ (=
_Trionyx_) _subplana_ and _Trionyx sinensis_. I have not seen an
ascending process of the pterygoids on skulls of American softshells
as described by Loveridge and Williams (_op. cit._:414, 429, fig. 54)
for _Lissemys_, _Cyclanorbis_, _Cycloderma_ and some _Trionyx
triunguis_.

_Opisthotic Wing_

This term refers to the laterally directed, posterior part of the
opisthotic that is visible in occipital, lateral and ventral views. In
ventral view the opisthotic wing is most easily seen and is wider in
_muticus_ than in _spinifer_ or _ferox_. In _muticus_ the distal part
is truncate, whereas in _ferox_ and _spinifer_, it is more tapered and
gently rounded, although somewhat unevenly flared medially. Also
there is more of a downward curvature (in ventral view) of the
opisthotic wing in _muticus_ than in _ferox_ or _spinifer_;
consequently the tip of the wing in _muticus_ is often just visible in
dorsal view (on lateral side of squamosal), certainly in lateral view.
The distal part or tip of the opisthotic wing is not visible in dorsal
view on skulls of _ferox_ or _spinifer_.

_Articular Surface of Quadrate_

The ventral surface of the quadrate that articulates with the mandible
is composed of a lateral condyle and a medial articular surface. The
condyle and medial articular surface are separated by a furrow. On
skulls of _ferox_ and _spinifer_ the lateral condyle, which is not
conspicuously tapered posteriorly, is slightly larger than the medial
articular surface, and the furrow is shallow. On skulls of _muticus_,
the lateral condyle is conspicuously tapered posteriorly, is slightly
smaller than the medial articular surface, and the furrow is deep.

_Contact of Maxillaries Above Premaxillaries_

The contact of the maxillaries above the premaxillaries is of
diagnostic value in distinguishing skulls of _ferox_ and _spinifer_
from those of _muticus_. I have seen no skulls of _muticus_ on which
the maxillaries were in contact, and no skulls of _ferox_ on which the
maxillaries were separated. Stejneger (1944:19), however, reported a
skull of _muticus_ (USNM 102677) having the maxillaries in contact.
Maxillaries are in contact (sometimes just barely) in 65 of 74 skulls
of _spinifer_ (88%); the premaxillaries are separated on nine skulls
(12%).

_Carapace_

The dorsal surface of the bony carapace of American trionychids
consists of a nuchal, seven or eight pairs of pleurals, and seven or
eight, rarely nine, neurals (Fig. 16). The lateral parts of the nuchal
overlie the second pair of ribs. The distal parts of the second
through the ninth pair of ribs extend laterally beyond the lateral
edges of the pleurals. There are no marginal ossifications. The
posterior part of the bony carapace bears blunt, rounded or ovoid to
linear, prominences mostly on the last pair of pleurals principally on
large females of _spinifer_ and _ferox_; I have seen only one adult
male (stuffed, MCZ 46633) having a semblance of welts on the bony
carapace. The nuchal, pleurals and neurals are sculptured.

As growth proceeds, the single, transversely-oriented, fontanelle of
young turtles that separates the nuchal from the first neural and
first pair of pleurals divides into two fontanelles that generally
decrease in size and finally disappear. Occasionally only one
(unilateral) large fontanelle is present (USNM 54734, _muticus_). The
largest specimens noted that retain fontanelles are a _ferox_ (USNM
029474) having a plastron 24 centimeters long, and a _spinifer_ (USNM
54731) having a plastron 20 centimeters long. The fontanelles probably
are present in some larger individuals.

[Illustration: FIG. 16. Carapace of _Trionyx spinifer_ (a), and
sketches of posterior parts of carapaces (b-i) of three American
species, showing number and variation in arrangement of neurals and
pleurals (not to scale; seventh neural, n7, and pleural, p7).

a. KU 2226, Lewisville, Lafayette County, Arkansas (× 1/3);
sculpturing incompletely shown. Labels: r, ribs; nu, nuchal; n,
neurals 1-7; p, pleurals 1-7.

b. _ferox_, USNM 60496, Auburndale, Polk County, Florida.

c. _muticus_, KU 1964, Doniphan Lake, Doniphan County, Kansas.

d. _spinifer_, USNM 100380, Plaquemine, Iberville Parish,
Louisiana.

e. _muticus_, TCWC 7260, Red River, 8 mi. NW Ringgold, Montague
County, in Clay County, Texas.

f. _spinifer_, USNM 59266, Homer, Winona, Minnesota.

g. _muticus_, KU 2840, White River, DeValls Bluff, Prairie County,
Arkansas.

h. _muticus_, USNM 115939, Mississippi.

i. _muticus_, USNM 54734, Mississippi River, Fairport, Muscatine
County, Iowa.
]

Most variation concerns the number of neurals and pairs of pleurals, and
their arrangement posteriorly (H. M. Smith, 1947:121, table; Stejneger,
1944:18). Table 5 shows the frequency of occurrence of the number of
neurals, pairs of pleurals, and the separation or contact of the seventh
pair of pleurals; figure 16 illustrates some of the configurations of
these plates posteriorly (e, g, and i not included in Table 5). The
eighth pair of pleurals is reduced or absent (Loveridge and Williams,
1957:417). Eight neurals and eight pairs of pleurals occur in all three
species. The seventh pleurals may contact each other in all three
species, and their separation has been observed only in the species
_spinifer_ and _muticus_. Seven neurals and contact of the seventh pair
of pleurals, or eight neurals and separation of the seventh pair of
pleurals from each other occurs with approximately equal frequency in
the species _muticus_. _T. ferox_ and _spinifer_ most often have seven
neurals, seven pairs of pleurals, and the seventh pair of pleurals in
contact. Stejneger (_loc. cit._) mentioned a specimen in MCZ having nine
neurals; I recorded nine neurals for USNM 54734 (Fig. 16i) for which
Stejneger (_loc. cit._) recorded eight. AMNH 57384 (_ferox_) has a small
eighth pleural on the left side only, and USNM 115939 (_muticus_) has an
eighth pleural only on the right side (Fig. 16h). Anomalous conditions
observed included: an accessory bone between the first and second
pleurals on the right side that contacts the first and second neurals in
USNM 54733, (_muticus_); only six neurals in USNM 95193 (_spinifer_); a
small accessory bony element between the first and second neurals in
AMNH 57383 (_ferox_); and, only six pleurals (second and third fused) on
the right side in USNM 54734 (_muticus_).

TABLE 5. Frequency of Occurrence of Number of Neurals, Pairs of
Pleurals, and Separation or Contact of the Seventh Pair of
Pleurals Among Species of American Soft-shell Turtles

===================+=================+==================================
Number | Contact (+) or | Species
--------+----------+ separation (-) +---------+------------+-----------
| Pairs of | of seventh pair | _ferox_ | _spinifer_ | _muticus_
Neurals | pleurals | of pleurals | (16) | (60) | (34)
--------+----------+-----------------+---------+------------+-----------
7 | 7 | + | 9 (56%) | 50 (83%) | 13 (38%)
7 | 8 | + | 5 (31%) | 2 (3%) | 2 (6%)
8 | 7 | + | 2 (13%) | 3 (5%) | 3 (9%)
8 | 8 | + | | 4 (7%) | 2 (6%)
8 | 7 | - | | 1 (2%) | 14 (41%)
--------+----------+-----------------+---------+------------+-----------

Ventrally, the bony carapace shows ten thoracic vertebrae, the second
through the ninth having well-developed, depressed ribs that are fused
(no sutures) to the pleurals. The ribs of the first thoracic vertebra
are represented by bony struts that extend posterolaterally and
contact the anterior borders of the second pair of ribs. The two ribs
of the ninth pair are free for most of their length and often are
broken; they are slightly shorter than the eighth pair of ribs. The
ribs of the tenth thoracic vertebra may be well-developed (KU 2219,
2666, 50856, _spinifer_, and 16528, _ferox_), but are usually broken
off and represented only by transverse processes.

Kyphosis

Kyphosis (angular curvature of the vertebral column) or the
hump-backed condition in American softshell turtles has been
summarized by Nixon and Smith (1949:28). Cahn (1937:185, pl. 25e)
illustrated the condition in an individual of _T. spinifer_, and H.
M. Smith (1947:119) mentioned kyphotic softshells representing the
species _spinifer_ (subspecies _hartwegi_ and _emoryi_) and _muticus_.
Neill (1951:10) mentioned two kyphotic _T. s. asper_ and Nixon and
Smith (_loc. cit._) recorded the report of a kyphotic _T. ferox_. I
have noted the condition in four _muticus_ (subspecies _muticus_, KU
1959-60, 23230; INHS 2148) and seven _spinifer_ (CNHM 22925;
subspecies _hartwegi_, USNM 55689; subspecies _spinifer_, UMMZ 52948,
95615; subspecies _emoryi_, KU 2219, 33523, TU 16240). The smallest
kyphotic specimen, a hatchling, TU 16240, has a plastral length of 3.5
centimeters. Kyphosis is to be expected in all kinds of softshells as
are other abnormalities, such as albinism (reported for _Lissemys_ by
D'Abreu, 1928, and partial albinism noted in _T. cartilagineus_ by
Mohr, 1929) or congenital absence of limbs (reported by Dutta, 1931,
as occurring in the genera _Trionyx_ and _Lissemys_). The cause of
kyphosis is not known. Smith (_op. cit._:120) suggested an abnormally
early fusion of the costals (= pleurals) with the ribs, and a
subsequent differential rate of growth between them and the vertebral
column as a hypothesis; Williams (1957:236) proposed that late
retraction of the yolk mass, or retraction of an excessively large
yolk mass may cause kyphosis. The cause of kyphosis may be of genetic
origin or due to some environmental damage to the vertebral column
prior to the cessation of growth. The variation in rate of growth of
the vertebral column may produce humps of different shapes and sizes.
Some of the specimens noted above (UMMZ 52948, 95615) have the
carapace only slightly arched and are considered partly kyphotic.
There seem to be degrees of kyphosis, a fact that should be taken into
account in considering the occurrence of variation in greatest depth
of shell.

Plastron

The plastron is united to the carapace by ligamentous tissue and is
somewhat flexible anteriorly and posteriorly. Anteriorly the plastron
is somewhat hingelike and may contact the anteriormost edge of the
carapace. The bony elements are reduced. There is usually a median
vacuity, which is relatively smaller in larger specimens and may be
divided into two vacuities (a posteromedial and an anteromedial) by
the medial juxtaposition of the hyo-hypoplastra, especially in
_muticus_. Williams and McDowell (1952) have recommended a change in
nomenclature for some of the plastral bones on the basis of
reinterpretation of their homologies. The nine plastral bones include:
an anterior pair of preplastra (= epiplastra, _auct._); an unpaired,
median bone, representing fused epiplastra (= entoplastron, _auct._),
hereafter referred to as the epiplastron; a pair of hyoplastra; a pair
of hypoplastra; and, posteriorly, a pair of xiphiplastra (Fig. 17).

Siebenrock's (1902) synopsis of living trionychids was based entirely
on plastral characters. He distinguished between _muticus_ and
_spinifer_ principally by the shape of the epiplastron; _T. ferox_ was
not considered different from _spinifer_. The median angle formed by
the boomerang-shaped epiplastron is obtuse and somewhat greater than
90 degrees in _muticus_ (Fig. 17a); the angle of the epiplastron in
_spinifer_ and _ferox_ is smaller than in _muticus_ and forms an
approximate right angle (Fig. 17b). Williams and McDowell (_op.
cit._:277, Pl. 1, Fig. 3) presented an illustration of the anterior
plastral elements of an adult _T. ferox_. Siebenrock provided
illustrations of the plastrons of _muticus_ (_op. cit._:823, Fig. 5)
and _spinifer_ (_op. cit._:830, Fig. 10).

[Illustration: FIG. 17. Plastron of _Trionyx muticus_ (a) and _T.
spinifer_ (b); sculpturing of callosities incompletely shown. ep,
epiplastron; hp, hyoplastron; hyp, hypoplastron; pp, preplastron;
xp, xiphiplastron. a--KU 1868, White River, Devall's Bluff, Prairie
County, Arkansas (× 2/3); b--KU 1869, same locality (× 2/3).]

Much importance has been credited to the fusion (no suture) or
separation (suture present) of the hypoplastra and hyoplastra. The
fusion of these bones distinguishes the genera _Lissemys_, _Cyclanorbis_
and _Cycloderma_ from _Trionyx_, _Pelochelys_, and _Chitra_ (Siebenrock,
_op. cit._:815, 817; Loveridge and Williams, 1957:415). This character
is also one of the criteria used by Hummel (1929: 768) in his erection
of the two subfamilies Cyclanorbinae (= Lissemyinae) and Trionychinae.
In my examination of specimens this character, unfortunately, was not
given full attention. I have noted the fusion of the hypoplastra and
hyoplastra in KU 1878 (_muticus_, right side only), KU 2219 (kyphotic
_spinifer_), KU 16528 (_ferox_) and KU 60121 (_ferox_). Dr. Ernest E.
Williams informs me in a letter of November 17, 1959, that of six
specimens of _ferox_ in the MCZ, the hyoplastra are fused with the
hypoplastra in three (54689-90, 54686). I suspect that these bones in
the three American species of the genus _Trionyx_, especially in
_ferox_, fuse more often than is supposed.

In _muticus_ the constricted part of the hyoplastron and hypoplastron is
wider anteroposteriorly than in _spinifer_ or _ferox_ (Fig. 17).

The three American species have on the hyoplastra, hypoplastra, and
xiphiplastra well-developed callosities, which enlarge with increasing
size. The medial borders of the hyoplastral and hypoplastral callosities
in larger specimens are rounded and closely approximated, often
touching, as do the callosities of each xiphiplastron; seemingly, the
callosities are relatively larger in _muticus_ than in _spinifer_ and
_ferox_. I have seen one adult male _muticus_ (KU 41380) that lacked
median fontanelles or vacuities owing to the contact of the plastral
elements (as viewed through overlying skin, alcoholic specimen). The
bony plastron (approximately 9 cm. in maximal length) of a small
_muticus_ (KU 19460) resembles the plastron of larger individuals of
_muticus_ in having well-developed hyoplastral and hypoplastral
callosities that are closely approximated medially. Large individuals of
_muticus_ usually have small, ovoid callosities on the preplastra, and a
well-developed, angular callosity on the epiplastron (Fig. 17a).
Siebenrock (_op. cit._:823) suggests that the presence of callosities on
the preplastra and epiplastron of _muticus_ is subject to individual
variation. I can not substantiate or dispute the supposition of Baur
(1888:1122), Siebenrock (1924:193) and Stejneger (1944:12, 19) that the
callosities are larger in males of _muticus_ than in the females. Some
individuals of _spinifer_ have seven plastral callosities (KU 2842) as
does _muticus_, but the callosities on the preplastra and epiplastron
are less frequent and less well-developed in large specimens of
_spinifer_ than in _muticus_. The small epiplastral callosity in
_spinifer_ is located at the medial angle and does not extend
posterolaterally to cover the entire surface of the epiplastron as it
may in _muticus_ (Fig. 17b). The epiplastron of a _spinifer_ (KU 2826)
has a medial callosity and another on the right posterolateral
projection; three separate callosities occur on the epiplastron of MCZ
46615. The last specimen mentioned, a large, stuffed female, possesses a
round, intercalary bone that tends to occlude the posteromedial vacuity.
Seemingly, the callosity on the epiplastron appears prior to those on
the preplastra; I have not seen any plastra having callosities on the
preplastra and lacking a callosity on the epiplastron. I have not noted
callosities on the preplastra or epiplastron of specimens of _ferox_.

The callosities on the plastral bones are sculptured; small, recently
formed callosities on the preplastra and epiplastron lack sculpturing.
The pattern of sculpturing on the plastral bones as well as that of the
carapace is generally of anastamosing ridges. I am unable to discern any
differences in pattern of sculpturing between the three American
species. Stejneger distinguished adult specimens of _ferox_ from the
other American species by the coarseness of the sculpture of the bony
callosities (1944:24) and of the bony carapace (_op. cit._:32). The
sculpturing on the plastral callosities and carapace seems to be
correlated with size; larger specimens (_ferox_) have coarser
sculpturing than do smaller specimens (_muticus_). Stejneger also
mentioned that the sculpturing on many specimens of _ferox_ is
specialized into prominent, longitudinal welts (_loc. cit._); these
welts occur also on the carapace of _spinifer_.

On the basis of the osteological characters examined by me, _T. muticus_
is distinguished from _spinifer_ and _ferox_ by a number of characters
(plastron and especially skull) whereas the species _spinifer_ and
_ferox_ are not easily distinguished from one another.

Composition of the Genus _Trionyx_ in North America

Analysis of the characters previously mentioned and their geographic
distribution permits the recognition of ten taxa, comprising four
species and eight subspecies. Two subspecies, _T. spinifer_ pallidus
and _T. s. guadalupensis_ are described as new. The four species and
the included subspecies here recognized are:

_Trionyx ferox_
_Trionyx spinifer spinifer_
_hartwegi_
_asper_
_emoryi_
_guadalupensis_
_pallidus_
_Trionyx ater_
_Trionyx muticus muticus_
_calvatus_

The following key is designed to permit quick identification of living
individuals; therefore, ratios and osteological characters are avoided
as much as possible in favor of other characters that are the least
variable and most "typical." Because there is considerable variation
correlated with sex and size, each taxon occurs in the key in more
than one couplet. Large females having mottled and blotched patterns
will be the most difficult to identify. The characters listed should
be used in combination because one character alone may not be
sufficient; it is advisable to read both choices of each couplet. The
text, figures and illustrations should be consulted for final
identification.

ARTIFICIAL KEY TO NORTH AMERICAN SPECIES AND SUBSPECIES OF THE GENUS
TRIONYX

1. Septal ridges present; tubercles on anterior edge of
carapace present or absent 2

Septal ridges absent; anterior edge of carapace lacking
tubercles or raised prominences 19

2. Plastral area a uniform dark slate or blackish; soft
parts of body blackish having large pale marks dorsally;
carapace having large black blotches, often fused along
margin, on pale background, and many well-defined
longitudinal ridges _ T. ferox_, p. 479

Combination of characters not as above; ventral
surface whitish, blackish flecks or blotches
sometimes present 3

3. Carapace having pattern of white dots, or black ocelli
and/or spots; carapace sometimes gritty resembling
sandpaper 4

Carapace uniform pale brownish or grayish, or having
mottled and blotched pattern, contrasting or not; white
dots or tubercles, black ocelli and/or spots may be
present; carapace not gritty 10

4. Carapace having pattern of black ocelli and/or spots;
numerous, conspicuous whitish spots or tubercles absent 5

Carapace having pattern of white dots that are sometimes
surrounded by small black ocelli; small black dots may be
interspersed among larger white dots 7

5. Carapace having two or more marginal lines, these often
diffuse and interrupted; black spots sometimes ocellate
or bacilliform, or interspersed among smaller black dots;
postocular and postlabial stripes usually united
_spinifer asper_, p. 502

Carapace having only one dark marginal line; pattern of
black ocelli or spots; postocular and postlabial stripes
usually not united 6

6. Carapace having prominent ocelli, which are much larger
near the center than at the sides
_spinifer spinifer_, p. 489

Carapace having numerous small, dark spots, sometimes
small ocelli, which are not much larger near the center
than the sides _spinifer hartwegi_, p. 497

7. White spots on anterior third of carapace; white spots
on carapace often surrounded by narrow blackish ocelli;
small black dots sometimes interspersed among white spots
_spinifer guadalupensis_, p. 517

White spots absent on anterior third of carapace, or
small and inconspicuous; white spots not surrounded
by narrow blackish ocelli 8

8. Pale rim of carapace narrow, partly obscured; over-all
dorsal coloration (including soft parts of body) dark and
lacking pattern; few, small, white tubercles confined to
posterior third of carapace _ater_, p. 528

Pale rim distinct, without markings; soft parts of body
dorsally not uniformly dark; many white tubercles
usually contrasting on pale carapace 9

9. White spots confined to posterior third of carapace;
ground color of carapace usually pale brown or tan,
sometimes darker; a dark, slightly curved, line
connecting anterior margins of orbits; postocular stripe
usually interrupted leaving pale, blotch behind eye;
pale rim of carapace four or five times wider
posteriorly than laterally _spinifer emoryi_, p. 510

Small white spots on posterior half of carapace gradually
decreasing in size anteriorly, often indistinct or absent
on anterior third of carapace; pale rim of carapace no
more than three times wider posteriorly than laterally
_spinifer pallidus_, p. 522

10. Marginal ridge present; carapace having ill-defined
dark blotches on uniform grayish, lacking whitish
tubercles or well-defined black spots or ocelli; pale
rim of carapace absent; tubercles on anterior edge of
carapace resembling flattened hemispheres; anterior
parts of plastron often visible in dorsal view;
postocular stripe, if present, having thick, blackish
borders _ferox_, p. 479

Marginal ridge absent 11

11. Carapace uniform pale brownish, lacking mottled and
blotched pattern, white dots, black ocelli or spots 12

Carapace having mottled and blotched pattern,
contrasting or not; white spots or tubercles, black
ocelli or spots may be present 13

12. Pale rim of carapace four or five times wider
posteriorly than laterally; dark, straight or slightly
curved, line connecting anterior margins of orbits
_spinifer emoryi_, p. 510

Pale rim of carapace no more than three times wider
posteriorly than laterally _spinifer pallidus_, p. 522

13. Rear margin of carapace usually roughened by fine
corrugations, edge often ragged; pale rim absent;
carapace having dark brown-blackish, mottled and
blotched pattern; anterior edge of carapace more or
less smooth having scarcely elevated prominences;
posterior part of plastral area and especially ventral
surface of carapace having numerous black marks
_ater_, p. 528

Rear margin of carapace smooth, edge entire;
usually some evidence of pale rim 14

14. White, rounded tubercles or spots usually evident
posteriorly on carapace, sometimes indistinct; black
ocelli or spots lacking in center of carapace,
sometimes present at sides; shape of tubercles on
anterior edge of carapace variable 15

White spots or tubercles absent; margin of carapace
usually having black ocelli or spots; tubercles on
anterior edge of carapace equilateral or conical,
not low and flattened 17

15. White spots often present on anterior half of carapace;
tubercles on anterior edge equilateral and wartlike,
or less elevated, not conical
_spinifer guadalupensis_, p. 517

White spots usually absent on anterior half of
carapace, sometimes indistinct; shape of tubercles
on anterior edge of carapace variable 16

16. White spots absent on anterior half of carapace;
tubercles on anterior edge of carapace low, scarcely
elevated, never equilateral or conical; mottled and
blotched pattern often not contrasting; ground color of
carapace sometimes dark; pale rim of carapace four or
five times wider posteriorly than laterally; dark,
straight or slightly curved, line connecting anterior
margins or orbits _spinifer emoryi_, p. 510

White spots sometimes indistinct on carapace, or few,
small spots present on posterior half of carapace;
tubercles on anterior edge of carapace equilateral and
wartlike or conical; mottled and blotched pattern usually
contrasting; pale rim less than three times wider
posteriorly than laterally _spinifer pallidus_, p. 522

17. Carapace having evidence of more than one dark marginal
line, and scattered, black spots or ocelli
_spinifer asper_, p. 502

Carapace having only one, dark, marginal line 18

18. Carapace having small black spots, lacking large
interrupted ocelli _spinifer hartwegi_, p. 497

Carapace having small black spots interspersed among
larger, interrupted ocelli _spinifer spinifer_, p. 489

19. Carapace having pattern of dusky spots, sometimes
short lines 20

Carapace lacking pattern of dark spots or lines,
having a mottled and blotched pattern 21

20. Pattern of circular spots, lacking short lines or
bacilliform marks; spots sometimes slightly ocellate;
no pale stripes on snout _muticus calvatus_, p. 539

Pattern of dots, or dots and short lines; pale
stripes on snout, at least just in front of eyes
_muticus muticus_, p. 534

21. Mottled and blotched pattern usually contrasting;
ill-defined, blackish blotch absent behind eye
_muticus muticus_, p. 534

Mottled and blotched pattern usually not contrasting;
ill-defined, dark blotch may be present behind eye
_muticus calvatus_, p. 539

Systematic Account of Species and Subspecies

=Trionyx ferox= (Schneider)

Florida Softshell

Plates 31 and 32

_Testudo ferox_ Schneider, Naturg. Schildkr., p. 330, 1783 (based
on Pennant, Philos. Trans. London, 61 (Pt. 1, Art. 32): 268,
pl. 10 [figs. 1-3], 1772).

_Trionyx ferox_ Schwartz, Charleston Mus. Leaflet, No. 26:17,
pls. 1-3, May, 1956.

_Testudo mollis_ Lacépède, Hist., Nat. Quadr. Ovip. Serp., 1:137,
pl. 7, 1788.

_Testudo_ (_ferox_?) verrucosa Schoepff, Hist. Testud., Fasc. 5
(Plag. M):90, pl. 19, 1795.

_Testudo bartrami_ Daudin, Hist. Nat. Rept., 2:74, pl. 18, fig. 2,
1801.

_Trionyx georgicus_ Geoffroy, Ann. Mus. Hist. Nat., Paris, 14:17,
August, 1809.

_Mesodeca bartrami_ Rafinesque, Atlan. Jour., Friend Knowledge,
Philadelphia, 1 (No. 2, Art. 12):64, Summer, 1832.

_Trionyx harlani_ Bell in Harlan, Medic. Phys. Research, p. 159,
1835.

_Type._--Holotype, British Museum (Natural History) 1947.3.6.17; original
number 53A, presumably that of Royal Society; stuffed adult female and skull;
obtained from the Savannah River, Georgia, by Dr. Alexander Garden.

_Range._--Southern South Carolina, southeastern Georgia, and all of Florida
except the Keys and perhaps the western end of the panhandle (see map, Fig.
18).

[Illustration: FIG. 18. Map of southeastern United States showing geographic distribution
of _Trionyx ferox_.]

_Diagnosis._--Marginal ridge present; longitudinal rows of tubercles that
resemble ridges on carapace of hatchlings; plastron often extending farther
forward than carapace in adults; plastral area dark slate or gray in hatchlings;
juvenal pattern of large slate or blackish blotches (often with pale centers)
on a pale background; pale outer rim of carapace (absent on adults) narrow,
not separated from ground color of carapace by distinct, dark line.

Size large; head wide; carapace relatively long and narrow; snout short;
greatest width of skull at level of quadratojugal; often no suture between
hypoplastra and hyoplastra; callosities on epiplastron and preplastra usually
lacking.

_Description._--Plastral length of smallest hatchling, 2.9 centimeters (UMMZ
95613), of largest male, 26.0 centimeters (AMNH 63642), of largest female,
34.0 centimeters (UMMZ 38123).

Septal ridges present; over-all coloration of carapace and plastron, and soft
parts of body of hatchlings slate or blackish; carapace having blackish, circular
blotches, usually fused at margin, often with pale centers on buff background
forming coarse reticulum; pale, narrow rim of carapace not separated from
ground color by dark marginal line; pale rim, coincident with marginal ridge,
absent from anteriormost nuchal region; longitudinal rows of tubercles on
carapace resembling ridges; undersurface blackish, usually having posterior part
of carapace pale with irregular blackish marks; blackish soft parts of body
dorsally having large, pale markings, most consistent of which are postocular
mark that may contact orbit, postlabial mark that curves around angle of jaws,
inverted Y on top of snout, and one or two streaks on side of neck.

Over-all coloration of adults grayish, paler than in hatchlings; carapace gray
sometimes having slightly darker, large, irregular markings; mottled and
blotched pattern on females not contrasting; sex of many large individuals not
distinguishable on basis of pattern on carapace; pale rim of carapace obscure or
absent; soft parts of body dorsally gray or brownish on large adults of both
sexes, sometimes having slightly paler, large markings; small adult males usually
having contrasting pattern on head; surface of carapace smooth (not "sandpaper")
on adult males; undersurface whitish, throat often grayish; well-defined
marginal ridge; anterior edge of carapace laterally to region of insertion
of forelimbs studded with low, flattened tubercles resembling hemispheres, never
conical; carapace usually having blunted tubercles, best developed anteriorly
and posteriorly on midline, but sometimes linearly arranged, resembling ridges,
especially at margins; anterolateral parts of plastron often extending farther
forward than corresponding parts of carapace.

Range in length (in cm.) of plastron of ten largest specimens of each sex
(mean follows extremes), males, 17.0-26.0, 20.0; females 23.3-34.0, 27.9;
ontogenetic variation in PL/HW, mean PL/HW of specimens having plastral
lengths 6.5 centimeters or less, 3.52, and exceeding 6.5 centimeters, 4.87;
ontogenetic variation in CL/CW, mean CL/CW of specimens having plastral
lengths 8.0 centimeters or less, 1.18, and exceeding 8.0 centimeters, 1.30; mean
CL/PCW, 2.01; mean HW/SL, 1.44; mean CL/PL, 1.26.

Jaws of some skulls that exceed 75 millimeters in basicranial length having
expanded alveolar surfaces; greatest width of skull usually at level of quadratojugal
(72%); ventral surface of supraoccipital spine narrow proximally, usually
having medial ridge; foramen magnum rhomboidal; opisthotic-exoccipital spur
absent (82%), sometimes indicated by ridge (16%); distal part of opisthotic wing
tapered, not visible in dorsal view; lateral condyle of articular surface of quadrate
larger than medial articular surface, not tapered posteriorly; maxillaries in contact
above premaxillaries; usually a combination of seven neurals, seven pairs
of pleurals, and contact of seventh pair of pleurals (56%), often eight pairs of
pleurals (31%); angle of epiplastron forming approximate right angle; often no
suture between hypoplastra and hyoplastra; callosities on preplastra and epiplastron
usually lacking.

_Variation._--Crenshaw and Hopkins (1955:19) stated that in specimens from
Lake Okeechobee and southward the carapace is wider relative to the width of
the head, and Neill (1951:19) quoted Allen's observations that _ferox_ from southern
Florida "average larger and darker than those collected farther north."

Carr (1952:417) reported that the pale reticulum on the carapace is yellowish
olive, the markings on head are yellow on an olive ground color, some
markings more orange, and the plastron slate gray. Duellman and Schwartz
(1958:271) mentioned that the carapace of hatchlings is edged in orange
grading to yellow posteriorly and has a pattern of bluish-black blotches on a
dull brown background, whereas the carapace is dull brown or blackish on
adults. Neill (_op. cit._:18) wrote "that the head stripes and the marginal
ring of the 'carapace' are orange rather than yellow (yellow at the time of
hatching, however)."

The transition from the dark coloration of hatchlings to the paler coloration
of adults is gradual and subject to individual variation. The loss of
dark color ventrally occurs first on the plastral area, then the hind limbs, forelimbs,
posterior part of carapace and last on the neck and throat. The soft
parts of the body dorsally are gray or dark gray, and do not become so pale
as the ventral surface. The smallest specimen that I have seen displaying the
dark features of the hatchlings is a male, 7.7 centimeters (UMMZ 100673);
a female, 9.5 centimeters (UMMZ 110987), is the smallest specimen having
a whitish plastral area. The change from dark to pale coloration on the ventral
surface occurs at a size of 8.0 to 9.0 centimeters. The largest specimens I
have seen having indistinct, dusky blotches of the underside of the carapace
are a female, 11.3 centimeters (UMMZ 100836), and a male, 16.0 centimeters
(UMMZ 106322). A contrasting pattern on head and limbs, and a
dark throat are still evident in a female 19.2 centimeters (UMMZ 106302).

_Comparisons._--_Trionyx ferox_ can be distinguished from all other species
of the genus in North America by the presence of a marginal ridge, longitudinal
ridges of tubercles on the carapace of juveniles (less evident in adults),
and the unique juvenal pattern and coloration. The lack of a juvenal pattern
and a smooth surface on the carapace (not gritty like sandpaper) distinguish
adult males from those of _T. spinifer_. Most adults of both sexes can be distinguished
from _spinifer_ and _muticus_ by the extension of the plastron farther
forward than the carapace (developed to a slight degree in some specimens
of _T. s. emoryi_). Both sexes of all ages can be distinguished from _muticus_ by
the presence of knoblike tubercles on the anterior edge of the carapace, and
septal ridges.

_T. ferox_ is the largest species in North America; the maximum size of the
plastron in adult males is approximately 26.0 centimeters (16.0 in _spinifer_)
and of adult females, 34.0 centimeters (31.0 in _spinifer_). The head is wider
in _ferox_ than in _muticus_ and most subspecies of _spinifer_ (closely approached
by _asper_, _guadalupensis_, _emoryi_ and _T. ater_). The carapace is narrower in
_ferox_ than in _muticus_ and most subspecies of _spinifer_ (closely approached by
_emoryi_ and _T. ater_). The snout is shortest in _ferox_, but almost as short in
_T. s. emoryi_ and _T. ater_. _T. ferox_ has proportionately the longest plastron in
relation to length of carapace.

Most skulls of _ferox_ differ from those of _muticus_ and _spinifer_ in having the
greatest width at the level of the quadratojugal (as do some _T. s. asper_; see
account of that subspecies). In the skull, _ferox_ resembles _spinifer_ but differs
from _muticus_ in having the 1) ventral surface of the supraoccipital spine narrow
proximally, and usually having a medial ridge, 2) foramen magnum rhomboidal,
3) distal part of opisthotic wing tapered, 4) lateral condyle of articular
surface of quadrate not tapered posteriorly, and larger than medial articular
surface, and 5) maxillaries in contact above premaxillaries. _T. ferox_ resembles
_muticus_ but differs from most individuals of _spinifer_ in lacking a well-developed
opisthotic-exoccipital spur. _T. ferox_ resembles _spinifer_ but differs from
_muticus_ in having the epiplastron bent at approximately a right angle; _ferox_
differs from both _muticus_ and _spinifer_ in lacking a callosity on the epiplastron
and probably in the more frequent fusion of the hyoplastra and hypoplastra.

_Remarks._--The early taxonomic history of _Trionyx ferox_ has been discussed
in detail by Stejneger (1944:27-32), who explained that Dr. Alexander
Garden of Charleston, South Carolina, sent a description and specimen of
_T. ferox_ to Thomas Pennant, and at the same time sent another specimen with
drawings to a friend, John Ellis, in London. Pennant presented one of the
specimens and drawings and the description to the Royal Society of London
in 1771; the description was published in 1772 and included Garden's drawings.
Because two specimens were involved the possibility exists that the
description (text, drawings and type specimen) is a composite based on two
specimens.

I have not seen the type. Garden's original description (_in_ Pennant, 1772:268-271)
leaves little doubt that the text subject is a large adult female of _ferox_
(see especially the statements, "fore part, [of carapace] just where it covers the
head and neck, is studded full of large knobs, [and] The under, or belly plate,
... is ... extended forward two or three inches more than the back
plate, ..."). I am indebted to Mr. J. C. Battersby, British Museum (Natural
History), Department of Zoology (Reptiles), for information concerning
the type and for comparing it with the text description and three figures published
by Pennant. The carapace of the type is approximately 16 inches long,
13-1/2 inches wide, and has low, flattened, knoblike tubercles along the anterior
edge. Some inaccuracies on the part of the artist (such as five claws on both
feet on the right side of Fig. 3, and four claws on the left front foot of Fig. 2 are
evident), and slight changes in the proportions of the type would have occurred
after death and preservation. It is the opinion of Mr. Battersby that the type,
text description and three figures represent one specimen. Figures 1 and 2,
dorsal and ventral views respectively, probably represent the same specimen
from life; the neck is withdrawn and the tail tip is visible in dorsal view, but
concealed beneath the posterior edge of the carapace in ventral view. Presumably
the same specimen (probably drawn from dried and stuffed animal)
is depicted in Figure 3 (dorsal view); the neck is fully extended and a large
part of the thick, pyramidal tail is visible in dorsal view. British Museum (Natural
History) 1947.3.6.17 is considered a holotype. The three figures published
by Pennant have been duplicated by Schoepff (1795:Pl. 19) and Duméril and
Bibron (1835:482). To my knowledge, the holotype was first specifically designated
as the "(Type.)" of _T. ferox_ by Boulenger (1889:259). The skull of the
holotype is figured by Stejneger (1944:Pl. 5).

Garden did not list a specific locality for the two specimens that he sent to
London, but did mention that the turtle was common in the Savannah and
Altamaha rivers (of Georgia), and rivers in east Florida. Boulenger (_loc. cit._)
stated that the locality of the holotype was "Georgia." Baur (1893:220) restricted
the type locality to the "Savannah river, Ga." Neill (1951:17), who
believed _T. ferox_ to be absent from the Savannah River, changed the type
locality of _ferox_ to east Florida. Schwartz (1956:8) reappraised the status of
softshells in Georgia and Florida and reëstablished the Savannah River (at
Savannah), Georgia, as the type locality of _T. ferox_.

Pennant failed to use binomial nomenclature when he published the type
description of Garden. The first name-combination (_Testudo ferox_) was proposed
by Schneider (1783:220).

Lacépède (1788:137, Pl. 7) referred to Garden's description in Pennant
only as "The Molle" but on a folded paper chart entitled "Table Méthodique
des Quadrupèdes ovipares," which is inserted after an introduction of 17 pages,
listed _T. mollis_; this name is again listed on another folded chart, entitled
"Synopsis methodica Quadrupedum oviparorum," which is inserted between
pages 618 and 619 under the genus _Testudo_. The illustration (Pl. 7) was
taken from Pennant (Duméril and Bibron, _loc. cit._). The type locality has
been designated "(following Stejneger, 1944) as eastern Florida" by Schmidt
(1953:108).

Bartram failed to use a binomial name with his description of "the great
soft shelled tortoise," which appeared in his _Travels_ (1791:177-179, Pl. 4 and
unnumbered plate between pages 282 and 283) and two editions of a French
translation (1799 and 1801, 1:307); see Harper (1940). Recently, Bartram's
_Travels_ has been placed on the Official Index of Rejected and Invalid Works
in Zoological Nomenclature, Opinion 447 (see Hemming, 1957). Bartram's
description of a soft-shelled turtle has provided the basis for the proposal of
at least three name-combinations. The first was _Testudo_ (_ferox?_) _verrucosa_
proposed in 1795 by Schoepff; it appeared simultaneously in _The Historia
Testudinum_ and in a German translation, _Naturgeschichte der Schildkröten_
(see Mittleman, 1944:245). Stejneger (1944:26) listed the type locality as
eastern Florida. Daudin (1801:74), also referring to Bartram's description
in his _Voyage_ (French translation), proposed the name _Testudo bartrami_;
Harper (_op. cit._:717) restricted the type locality of _T. bartrami_ from "Halfway
pond," east Florida, to southwestern Putnam County between Palatka
and Gainesville, Florida. Rafinesque (1832:64-65), relying on the authenticity
of the illustrations in Bartram's _Travels_ that depict a soft-shelled turtle
having five claws on each of the hind feet, tubercles on the sides of the head
and neck, and ten scales in the middle of the carapace (presumably inaccuracies
or a composite on the part of the artist), referred to Bartram's description as
a new genus, _Mesodeca bartrami_, a name which Boulenger (1889:245, footnote)
referred to as "mythical." Geoffroy (1809a:18-19) considered Bartram's
description the basis for the recognition of a second species of _Chelys_ (binomial
nomenclature not employed), and Duméril and Bibron (_loc. cit._) suggested
that the description was based partly on a "Chelyde Matamata."
The descriptive comments of Bartram are not clearly applicable to _Testudo
ferox_ Schneider; _Trionyx ferox_, however, is the only species of soft-shelled
turtle known to occur in the region of Bartram's observations (east Florida),
and the type locality was restricted to Putnam County, Florida, by Harper.
The name-combinations, _Testudo___ (_ferox?_) _verrucosa_ Schoepff, _Testudo bartrami_
Daudin, and _Mesodeca bartrami_ Rafinesque are junior synonyms of _Testudo
ferox_ Schneider.

Schweigger (1812:285) referred _ferox_ to the genus _Trionyx_ following the
description of that genus by Geoffroy in 1809. _Testudo ferox_ was listed as a
synonym by Geoffroy in the description of _Trionyx georgicus_ (1809a:17);
Duméril and Bibron (1835:432) mentioned that the specific characters of
_georgicus_ were taken from Pennant. The name _Trionyx georgianus_ presumably
appears for this taxon in Geoffroy's earlier-published synopsis (1809:367).
_T. georgicus_ was listed as occurring in rivers of Georgia and the Carolinas;
the type locality was restricted by Schmidt (_op. cit._:109) to the Savannah
River, Georgia. The two specific names _georgicus_ and _georgianus_ are regarded
as substitute names and junior synonyms of _T. ferox_.

Geoffroy (1809a:14-15) also described _Trionyx carinatus_, a name-combination
that hitherto has been considered a synonym of _Trionyx ferox_. There
is no indication from the description that _carinatus_ is applicable to _ferox_.
Most comments pertain to a description of the bony carapace and plastron,
which Geoffroy depicts in Plate 4. It is a young specimen judging from the
small and isolated preneural; the seventh pair of pleurals is unusual in being
fused (no middorsal suture), and the neurals seem large in proportion to
the size of the pleurals. The anterior border of the carapace is described
as having tubercles. Geoffroy listed _Testudo membranacea_ and _Testudo
rostrata_ as synonyms of _carinatus_. Fitzinger (1835:127) listed _T. membranacea_,
_T. rostrata_ and _T. carinatus_ as synonyms of _Trionyx javanicus_
(= _T. cartilagineus_), which was also described by Geoffroy (_op. cit._:15).
Duméril and Bibron (_op. cit._:478, 482) considered _carinatus_ to be the young
of _spinifer_ (_ferox_ as synonym). Gray (1844:48), however, referred _T. membranacea_
and _T. rostrata_ to the synonymy of _T. javanicus_, but considered _T.
carinatus_ to be a synonym of _T. ferox_ (_op. cit._:50), an interpretation followed
by all subsequent authors. _Trionyx carinatus_ is questionably listed as a
synonym of _ferox_ by Stejneger (1944:27). Duméril and Bibron (_op. cit._:482)
wrote that the young type of _carinatus_ is in the museum at Paris. Dr. Jean
Guibé informs me in letter of September 24, 1959, that the type of Geoffroy's
_T. carinatus_ cannot be found in the Natural History Museum at Paris. For
the present, _T. carinatus_ is considered a _nomen dubium_. According to Stejneger
(1944:27), _Trionyx brongniarti_ Schweigger is a substitute name for
_T. carinatus_.

I am unable to add anything to Stejneger's (_op. cit._:32) account of _Trionyx
harlani_; the mention of its occurrence in east Florida indicates that it is indistinguishable
from _Testudo ferox_ Schneider.

_T. ferox_ was considered to be indistinguishable from Lesueur's _Trionyx
spiniferus_ (described in 1827), until Agassiz (1857:401) pointed out the
differences between the two species. However, Agassiz (_op. cit._:402, Pl. 6, Fig.
3) regarded juveniles of _T. spinifer asper_ as the young of _ferox_. Consequently,
the geographic range of _ferox_, as envisioned by Agassiz, extended from
Georgia and Florida west to Louisiana. Neill (1951:15) considered all
American forms conspecific. Crenshaw and Hopkins (1955) and Schwartz
(1956) demonstrated that _ferox_ is a distinct species.

Fitzinger (1843:30) designated the species _ferox_ as the type species of
his genus _Platypeltis_ as follows: "Platypeltis. Fitz. Am[erica]. _Platypelt.
ferox_. Fitz. Typus." If populations of soft-shelled turtles that are referable
to _Testudo ferox_ Schneider are considered to comprise a distinct genus by
future workers, _Platypeltis_ Fitzinger, 1835, is available as a generic name with
_Testudo ferox_ Schneider, 1783, as the type species (by subsequent designation).

_Trionyx ferox_ in the northern part of its range is sympatric with _T. spinifer
asper_. In the region of overlap, the two species are nearly always ecologically
isolated; _ferox_ inhabits lentic waters, whereas _T. s. asper_ is partial to lotic
waters (Crenshaw and Hopkins, _op. cit._:16). There is no evidence of intergradation
or hybridization.

Many characters of _Trionyx ferox_ that are lacking in other North American
forms are shared with some Asiatic softshells, such as the large size, longitudinal
rows of tubercles that resemble ridges on the carapace, and the marginal
ridge. It is thought that, of the living softshells in North America, _ferox_ is
more closely allied to Old World forms of the genus than to _muticus_ or _spinifer_.

Carr (1940:107) recorded _ferox_ from Okaloosa County, Florida, in the western
end of the panhandle, whereas Crenshaw and Hopkins (1955:16) list the
known westward extent of range as Leon and Wakulla counties. AMNH 6933
from west of the Apalachicola drainage in Washington County, Florida, tends
to substantiate Carr's record, which is not included on the distribution map.

_Specimens examined._--Total 144, as follows: FLORIDA: _Alachua_: UMMZ
64178, 100969; USNM 10545, 10704, "near" Gainesville; UMMZ 56599, Levy
Lake. _Brevard_: AMNH 12878, Canaveral. _Broward_: UMMZ 109441, Hugh
Taylor Birch State Park; USNM 109548, 22 mi. WNW, 6 mi. SSE Fort Lauderdale.
_Collier_: USNM 86828, Tamiami Trail, "near" Birdon. _Dade_: AMNH
50936, UMMZ 10183, 110981, Miami; USNM 84079, 86942, 15 mi. from (west)
Miami, Tamiami Trail; UMMZ 111371, 19 mi. W, 1.3 mi. S Miami; UI 28984,
35 mi. W. (Miami) Tamiami Trail; AMNH 69932-33, UMMZ 101582, 101584,
104024, 40-45 mi. W Miami, Tamiami Trail. _Glades_: UMMZ 100836, mouth of
Kissimmee River. _Hendry_: UMMZ 106302, 10.2 mi. SE Devil's Garden;
UMMZ 106303-04, 106321-22, 30 mi. S Clewiston, near Devil's Garden.
_Hernando_: TU 13624, 0.5 mi. S Citrus Co. line on US Hwy. 19. _Highland_:
AMNH 65537, 71618, Archbold Biol. Stat., Lake Placid; AMNH 65622, Hicoria.
_Hillsborough_: TU 13960, Hillsborough River, _ca._ 20 mi. NE Tampa; USNM
51184, Tampa; USNM 71156, Plant City. _Indian River_: USNM 55316, Vero
Beach; USNM 59318, Sebastian. _Lake_: UMMZ 36072, USNM 20189, 029210,
029339, 38123, Eustis; UMMZ 76754-56, Lake Griffin. _Lee_: UMMZ 102276,
14 mi. SE Punta Gorda. _Leon_: CNHM 33701, USNM 95767, Lake Iamonia;
USNM 103736, Silver Lake. _Marion_: AMNH 8294-95, UMMZ 95613 (4),
USNM 52476-83, 100902-04, Eureka; AMNH 63642, near Salt Springs. _Martin_:
TNHC 1292, 8.4 mi. N Port Mayaca. _Okeechobee_: AMNH 57379-84, Lake
Okeechobee; AMNH 5931-32, Kissimmee Prairie. _Orange_: USNM 51421,
56805, Orlando; KU 16528. _Osceola_: USNM 029448, 029450-64, 029467-68,
029470, 029474-75, Kissimmee. _Palm Beach_: UMMZ 54101, Palm Beach;
USNM 73199, Delray Beach. _Pinellas_: USNM 51417-20, St. Petersburg. _Polk_:
AMNH 25543, Lakeland; UMMZ 112380, 6.7 mi. S Lake Wales; USNM 60496,
60532, 60534, 61083-87, Auburndale. _Putnam_: USNM 4373, 7651, Palatka;
USNM 26035, ponds "near" Welaka. _Sarasota_: USNM 61352, Lake Myakka.
_Sumpter_: UMMZ 71791, Bushnell. _Volusia_: UMMZ 100673, Lake Helen.
_Washington_: AMNH 6933, Washington. _County unknown_: AMNH 4758;
USNM 8899, St. John's River: USNM 59727-28, Lake Okeechobee, "near"
mouth Taylor's Creek; USNM 84080.

GEORGIA: _Baker_: SM 2083, USNM 029619, 38980-81, 70398, Mimsville.
_Berrien_: USNM 62217, Banks Mill Pond. _Charlton_: AMNH 69934, Okefinokee
Swamp, SW Billy's Island; UMMZ 90010, east edge Okefinokee Swamp; USNM
84603, Okefinokee Swamp, Chesser's Island. _Irwin_: USNM 56804. _Lowndes_:
UMMZ 67706, 10 mi. S Valdosta. _McIntosh_: USNM 19621, Darien.

SOUTH CAROLINA: _Charleston_: USNM 9670, Charleston.

NO DATA: AMNH 22750; USNM 71608-09.

_Records in the literature._--FLORIDA: _Alachua_: 10 mi. ENE Gainesville
(Schwartz, 1956:18). _Brevard_: Merritt Island (Neill, 1958:6). _Broward_:
Fort Lauderdale (Schwartz, _op. cit._:19). _Charlotte_: (Carr, 1940:107). _Clay_:
Green Cove Springs (Brimley, 1910:18); St. John's River (Crenshaw and Hopkins,
1955:21); Doctor's Inlet (Schwartz, _op. cit._:18). _Collier_: Royal Palm
Hammock (Crenshaw and Hopkins, _op. cit._:20); 11.2 mi. E Monroe Station
(Schwartz, _op. cit._: 19). _Columbia_: (Carr, _loc. cit._). _Dade_: Paradise Key
(Schwartz, _loc. cit._); Homestead (eggs, Stejneger, 1944:43). _Duval_: 4-10
mi. S Jacksonville (Deckert, 1918:31). _Glades_: _ca._ 8 mi. SW Okeechobee
State Park. _Lake_: Alexander Springs (Schwartz, _op. cit._:18). _Lee_: 18 mi.
S Fort Myers (Conant, 1930:63); 6 mi. SE Fort Myers (Hamilton, 1947:209).
_Levy_: Gulf Hammock (Schwartz, _loc. cit._); Brownson (Stejneger, _op. cit._:42).
_Monroe_ and _Okaloosa_ (Carr, _loc. cit._). _Okeechobee_: 6 mi. E Kissimmee River;
state hwy. 78 "near" Okeechobee-Glades co. line. _Palm Beach_: SW part of
Lake Okeechobee, near Clewiston; Milton Island Cove (Schwartz, _loc. cit._).
_Pasco_: mouth Pithlachascotee River (Neill, _op. cit._:26). _Pinellas_: Belleair
(Brimley, _loc. cit._); Seminole (Conant, _loc. cit._); 5 mi. E Clearwater (Schwartz,
_op. cit._:19); Gulf Port (Stejneger, _op. cit._:43). _Polk_: Lake Shipp, near
Winter Haven (Telford, 1952:185). _Sarasota_: 15 mi. E Sarasota (Conant,
_loc. cit._); Venice (Conant, _op. cit._:61). _Taylor_: "near" Foley. _Wakulla_:
"near" Crawfordville (Crenshaw and Hopkins, _op. cit._:15).

GEORGIA: _Baker_: 5 mi. NW Newton, 5 mi. W Newton, 4 mi. N Newton.
_Ben Hill_: 6 mi. E Fitzgerald (Crenshaw and Hopkins, 1955:15). _Bulloch_: 14
mi. SE Statesboro (Schwartz, 1956:19). _Decatur_: "near" Bainbridge (Crenshaw
and Hopkins, _loc. cit._). _Emanuel_: "near" Midville. _Evans_: 8 mi. NE
Manassas, Tattnall County. _Ware_: Laura Walker State Park (Schwartz, _loc.
cit._). _Wilcox_: 3 mi. SE Forest Glen (Crenshaw and Hopkins, _op. cit._:19).

SOUTH CAROLINA: _Beaufort_: 7 mi. NE Gardens Corner (Schwartz, 1956:19).
_Chatham_: Savannah River at Savannah (Schwartz, _op. cit._:8-9). _Colleton_: 5
mi. from Whitehall, Combahee River (Schwartz, _op. cit._:19).

=Trionyx spinifer= Lesueur

Spiny Softshell

_Range._--In Canada, southern Ontario and Quebec; in the United States,
northwestern Vermont and western New York south to northern Florida, east
to central Montana, eastern Wyoming and Colorado, and New Mexico; introduced
into the Colorado River system of California, Nevada, Arizona and New
Mexico; in México, the northern part of the states of Tamaulipas, Nuevo León,
Coahuila, and eastern Chihuahua (see map, Fig. 19).

_Diagnosis._--Juvenal pattern uniform tan or brownish lacking markings, having
whitish dots or spots, or having well-defined, blackish ocelli or spots; surface
of carapace "sandpapery" in adult males; conical projections (in some subspecies)
along anterior edge of carapace in large females; contrasting pattern of
blackish marks on pale background (in some subspecies) on dorsal surface of
limbs of adult males.

Opisthotic-exoccipital spur well-developed; epiplastral callosity, when present,
not covering entire surface.

_Description._--Septal ridges present; external and proportional characteristics
variable (see accounts of subspecies); range in length of plastron (cm.) of ten
largest specimens of each sex (mean follows extremes), males, 13.8-16.0, 14.4;
females, 26.0-31.0, 28.0.

[Illustration: FIG. 19. Geographic distribution of _Trionyx spinifer_.

Guide to subspecies:

1. _T. s. spinifer_
2. _T. s. hartwegi_
3. _T. s. asper_
4. _T. s. pallidus_
5. _T. s. guadalupensis_
6. _T. s. emoryi_
]

Greatest width of skull usually at level of squamosal (74%); foramen
magnum rhomboidal; ventral surface of supraoccipital spine narrow
proximally, usually having medial ridge; opisthotic-exoccipital spur
well-developed (66%); distal part of opisthotic wing tapered, not
visible in dorsal view; lateral condyle of articular surface of
quadrate larger than medial articular surface, not tapered
posteriorly; maxillaries in contact above premaxillaries (88%);
usually a combination of seven neurals, seven pairs of pleurals and
contact of seventh pair of pleurals (83%); angle of epiplastron
approximately 90 degrees; callosities when present on epiplastron not
covering entire surface; hyo-hypoplastral suture usually present.

_Comparisons._--_Trionyx spinifer_ can be distinguished from _T.
ferox_ and _T. muticus_ by the presence of any one of the characters
mentioned in the "Diagnosis." Both sexes and all sizes of _T.
spinifer_ resemble _ferox_ but differ from _muticus_ in having septal
ridges. Most individuals of _T. spinifer_ (except some large females)
resemble _muticus_ but differ from _ferox_ and large females of _ater_
in having a pale outer rim that is separated from the ground color of
the carapace by a distinct (_spinifer_) or dusky (_muticus_) dark
line. Large females of the subspecies _spinifer_, _hartwegi_, _asper_
and _pallidus_ may have enlarged conical projections along the
anterior edge of the carapace and, unless these projections are
considerably worn, are readily distinguished from large females of
_ferox_ (flattened, knoblike prominences), and _muticus_ and _ater_
(smooth surface, no prominences). Large females of the subspecies
_guadalupensis_ and _emoryi_ resemble _muticus_ and _ater_, and to
some extent _ferox_, in having low, scarcely elevated prominences
along the anterior edge of the carapace. Some females of _emoryi_
resemble _ferox_ in that the plastron extends farther forward than the
carapace.

_T. spinifer_ is intermediate in size between _ferox_ (larger) and
_muticus_ (smaller); the maximum size of the plastron in adult males
is approximately 16.0 centimeters (14.0, _muticus_; 26.0, _ferox_),
and of females, 31.0 centimeters (21.5, _muticus_; 32.5, _ferox_). The
head for all subspecies of _spinifer_ is proportionately narrower than
in _ferox_ but wider than in _muticus_.

In the skull, _spinifer_ more closely resembles _ferox_ than
_muticus_, but differs from both _ferox_ and _muticus_ in usually
having a well-developed opisthotic-exoccipital spur. Skulls of
_spinifer_ resemble those of _muticus_ but differ from those of
_ferox_ in being widest at the level of the squamosal. Skulls of
_spinifer_ resemble those of _ferox_ but differ from those of
_muticus_ in having the 1) ventral surface of the supraoccipital spine
narrow proximally, and usually having a medial ridge, 2) foramen
magnum rhomboidal, 3) distal part of opisthotic wing tapered, 4)
lateral condyle of articular surface of quadrate not tapered
posteriorly, and larger than medial articular surface, and 5)
maxillaries in contact above premaxillaries. _T. spinifer_ resembles
_ferox_ but differs from _muticus_ in having the epiplastron bent at
an approximate right angle. _T. spinifer_ differs from _ferox_ in
having an epiplastral callosity, and from _muticus_ in that the
callosity does not cover the entire surface of the epiplastron. The
hyo-hypoplastral suture is present more often in _spinifer_ and
_muticus_ than in _ferox_.

_Remarks._--Gray (1869:221) proposed the generic name _Callinia_ as a
new name for _Aspidonectes_ as understood by Agassiz (1857:403). Gray
referred _Trionyx spiciferus_ (= _spiniferus_) Lesueur to _Callinia_.
Stejneger (1907:514) designated _Trionyx spiniferus_ Lesueur as the
type species of _Callinia_. If _Trionyx spiniferus_ Lesueur is
considered to be generically distinct from other soft-shelled turtles,
_Callinia_ Gray, 1869, is available as a generic name with _Trionyx
spiniferus_ Lesueur, 1827, as the type species by subsequent
designation.

_Geographic variation._--_T. spinifer_ is the most variable and
widespread species of the genus in North America. Size of ocelli on the
carapace decreases from east to west on turtles inhabiting waterways of
the Upper Mississippi River drainage. The most impressive gradient,
geographically oriented from western Louisiana to southwestern Texas is
seen in each of several features: decrease in size of tubercles on the
anterior edge of the carapace, reduction in contrast of pattern on the
dorsal surface of limbs and side of head, change in pattern on the
dorsal surface of the snout, and increase in the size of white spots on
the carapace. But the gradient in size of white spots is reversed in _T.
s. emoryi_, which has small white spots on the carapace. Some of the
characters at the western terminus of this geographical gradient are
shared with _T. ater_ and _muticus_. Those subspecies comprising the
_emoryi_ group also show proportional characters that correspond closely
with those of _T. ferox_.

On the basis of tuberculation and pattern on carapace, side of head,
dorsal surface of limbs and snout, _Trionyx spinifer_ may be divided
into six subspecies.

=Trionyx spinifer spinifer= Lesueur

Eastern Spiny Softshell

Plates 33, 34, and 52

_Trionyx spiniferus_ Lesueur, Mém. Mus. Hist. Nat. Paris, 15:258,
pl. 6, December, 1827.

_T[rionyx] s[pinifer] spinifer_ Schwartz, Charleston Mus. Leaflet,
No. 26:11, May, 1956.

_Trionyx ocellatus_ Lesueur, Mém. Mus. Hist. Nat. Paris, 15:261,
December, 1827.

_Apalone hudsonica_ Rafinesque, Atlan. Jour., Friend Knowledge,
Philadelphia, 1(No. 2, Art. 12):64, Summer, 1832.

_Trionyx annulifer_ Wied-Neuwied, Riese Nord-Amerika, 1(pt. 3):140,
1838.

_Tyrse argus_ Gray, Cat. Tort. Croc. Amphis. Brit. Mus., p. 48,
1844.

_Aspidonectes nuchalis_ Agassiz, Contr. Nat. Hist. United States,
1(pt. 2):406, 1857.

_?G[ymnopus] olivaceus_ Wied-Neuwied, Nova Acta Acad.
Leopold.-Carol., 32:55, pl. 5, 1865.

_Type._--Lectotype, Museum d'Histoire Naturelle, Paris, No. 8808;
large stuffed female obtained by C. A. Lesueur from the Wabash River,
New Harmony, Posey County, Indiana (Pl. 52).

_Range._--Northeastern United States and extreme southeastern Canada
in tributaries flowing into the Mississippi River from the east, and
the St. Lawrence River drainage; extreme southern Quebec and Ontario,
Canada, east through southern Great Lakes region to Wisconsin, and
south through New York, western Pennsylvania and Illinois to Tennessee
and western Virginia (see map, Fig. 19).

_Diagnosis._--Juvenal pattern of large, thick-bordered black ocelli,
often 9-10 millimeters in diameter in center of carapace on adult
males, and 2-3 millimeters in diameter on hatchlings (mean OD/PL,
Michigan, .066); only one dark marginal line separating pale rim of
carapace from dorsal ground color.

_Description._--Plastral length of smallest hatchling, 2.7 centimeters
(UMMZ 89950, INHS 3143); of largest male, 14.5 centimeters (UMMZ
72512); of largest female, 31.0 centimeters (UMMZ 40866).

Carapace olive, having large ocelli in center but smaller ocelli or
spots at sides; ocelli often interrupted; pale rim of carapace not
four or five times wider posteriorly than laterally, separated from
darker ground color of carapace by one dark marginal line; large
females often having remnants of ocelli at sides of carapace on
mottled and blotched background; pattern on snout of pale,
dark-bordered stripes that unite forming acute angle in front of eyes;
well-defined dark markings in subocular and postlabial region; pattern
contrasting with ground color on side of head; postlabial stripe
interrupted, diffuse; pale postocular stripe having blackish borders
interrupted, not uniting with postlabial stripe; dorsal surface of
soft parts of body having contrasting pattern, largest blackish marks
on hind limbs; elongate tail of adult males having pale dorsolateral
bands with well-defined lower blackish borders; underparts whitish,
often having blackish marks, except in center of plastral area; dark
marks on webbing of limbs, palms and soles; dark streaks often
coincident with digits; small conical tubercles on anterior edge of
carapace on adult males; conical or equilateral tubercles on anterior
edge of carapace of large females; accessory knoblike tubercles in
nuchal region and in middle of carapace posteriorly on large females.

Ontogenetic variation in PL/HW, mean PL/HW of specimens having
plastral lengths 7.0 centimeters or less, 4.09, and exceeding 7.0
centimeters, 5.50; ontogenetic variation in CL/CW, mean CL/CW of
specimens having plastral lengths 8.5 centimeters or less, 1.12, and
exceeding 8.5 centimeters, 1.21; mean CL/PCW, 2.02; mean HW/SL, 1.30
(including subspecies _hartwegi_); mean CL/PL, 1.39.

_Variation._--Variant individuals include: UMMZ 72512, an adult male,
having some ocelli seven millimeters in diameter that are almost solid
spots; UMMZ 89659 having postocular and postlabial stripes connected
on right side of head; UMMZ 95615, 52948, 54402 having inner dark
borders of pale stripes on snout represented by short dashes and dots
(a ragged line connecting anterior margins of orbits on 54402); UMMZ
52948, 89659 having interrupted, black marginal lines on carapace with
ends of some segments oriented inward and overlapping portion of
adjacent segments; UMMZ 81699, female having plastral length of 19.0
centimeters, lacking conspicuous tubercles on anterior edge of
carapace; UI 2403, CNHM 92204 having extensive dark mottling and
marbling on throat and neck, undersurface of limbs and posterior
portion of carapace.

_Comparisons._--_T. s. spinifer_ can be distinguished from all other
subspecies of _T. spinifer_ by the presence of large black ocelli
(diameter 9-10 mm. on adult males, 2-3 mm. on hatchlings) in
combination with only one dark marginal line. _T. s. spinifer_
resembles _asper_ in having ocelli or dots on the carapace but differs
from _asper_ in having only one dark marginal line and larger ocelli.
_T. s. spinifer_ differs from _hartwegi_ only in the large size of the
ocelli. _T. s. spinifer_ resembles _hartwegi_ and _asper_ but differs
from _pallidus_, _guadalupensis_ and _emoryi_ in having blackish spots
and ocelli on the carapace and lacking whitish dots. _T. s. spinifer_
resembles _hartwegi_, _asper_, and _pallidus_ and differs from
_guadalupensis_ and _emoryi_ in having conical or knoblike tubercles
on the anterior edge of the carapace on large females.

_T. s. spinifer_ differs from the subspecies _asper_, _guadalupensis_
and _emoryi_ in having a relatively narrower head, and from _emoryi_
in having a relatively wider carapace. _T. s. spinifer_ resembles
_hartwegi_ and _asper_ but differs from the other subspecies in having
the carapace widest at a plane approximately one-half way back on the
carapace. The subspecies _spinifer_ and _hartwegi_ have longer snouts
than _pallidus_, _guadalupensis_, and _emoryi_. _T. s. spinifer_
differs from _asper_ but resembles all the other subspecies in having
a relatively longer plastron.

_Remarks._--Lesueur's description of _Trionyx spiniferus_
(1827:258-261, Pl. 6) seems to be based mostly, if not entirely, on a
large female (length of carapace, 13 inches), which was "Le plus grand
des individus observes ..." (_op. cit._:258); an accompanying
illustration depicting the dorsal surface of the bony carapace is
unusual in lacking neurals (Pl. 6, E). Duméril and Bibron (1835:481)
mentioned eight or nine additional specimens that Lesueur sent to the
Museum of Natural History in Paris. Dr. Jean Guibé informed me under
letter dated September 24, 1959, that a larger stuffed female, bearing
catalog number 8808 is regarded as the holotype, and that there are
seven additional specimens (1949, 4143, 8807, 8809-12) in the museum
at Paris. All turtles were obtained by Lesueur from the Wabash River.
To my knowledge no specimen that was available to Lesueur has been
specifically designated as a type. Because the description seems to be
based on one specimen, undoubtedly No. 8808, this specimen has been
regarded as the holotype. However, Lesueur referred to several
specimens and did not mention a type in the original description;
consequently I prefer to regard No. 8808 as a lectotype.

Lesueur also described _Trionyx ocellatus_ (_op. cit._:261-263) as a
variety of _T. spiniferus_ having ocelli, or parts thereof, on the
carapace and mentioned three specimens. The total number of specimens
that were available to Lesueur is unknown. One young alcoholic
specimen having ocelli is in the British Museum (Natural History)
(Gray, 1855:69). The same letter from Dr. Guibé stated that a specimen
in the Museum of Natural History, Paris, No. 6957, having a carapace
17 centimeters in length, conforms to the characters of _ocellatus_ as
mentioned by Lesueur, and was obtained from the Wabash River by
Lesueur. Two of the specimens mentioned by Lesueur (_loc. cit._) are
stated to be females. No. 6957 is an adult male and clearly shows the
juvenal pattern; it is regarded as the lectotype of _T. ocellatus_
Lesueur, a name-combination, which is a synonym, based on a secondary
sexual difference in pattern.

Rafinesque (1832:64) described a soft-shelled turtle from "the River
Hudson between the falls of Hadley, Glen and Baker, and further up to
the source" as _Apalone hudsonica_. The most outstanding
characteristic was the presence of five claws on the digits of each
limb. Rafinesque's recording of this characteristic was perhaps
influenced by the illustration of a softshell in Bartram's _Travels_
that showed each limb with five, clawed digits. Perhaps this was the
basis for Boulenger (1889:245, footnote) regarding _Apalone_ as
"mythical." The large, yellowish, black-bordered spots, one behind and
one in front of the eye presumably represent segments of the
postocular stripe and the stripe on the snout; Rafinesque described
the carapace as "entire ... the margin is yellowish unspotted, then
comes a circular black line ..." and having "many round spots
occulated and clouded by having a brown margin, with grey dots
within." Except for five claws, the description is applicable to a
softshell and referable to _T. s. spinifer_. To my knowledge, the only
other records of the occurrence of soft-shelled turtles in the Hudson
river drainage are those of Eights (_in_ Bishop, 1923:120, Mohawk
River at Cohoes), and DeKay (1842:7, Mohawk River and Hudson River
near Albany); presumably these records are the basis for the comments
of Holbrook (_in_ Bishop, _loc. cit._), and symbolized as an isolated
locality by Conant (1958:318, map 35). The type locality of _Apalone
hudsonica_ is herein restricted to the Hudson River, near Baker's
Falls, Saratoga County, New York.

Gray (1844:48) proposed the name _Tyrse argus_ for a specimen reported
to have come from Sierra Leone, West Africa; later (1855:68), he
referred the species to the genus _Trionyx_. After comparison with a
specimen of _T. spiniferus_ Lesueur, Gray (1864:89) was "doubtful
whether there must not have been some confusion about the habitat of
the specimen [which formed the basis of the description of _Tyrse
argus_], and whether it is not more probably a North American
species." The same author (1869:222; 1870:109) listed _Tyrse argus_ as
a synonym of _Callinia spinifera_ (= _Trionyx spiniferus_ Lesueur).

Agassiz (_op. cit._:406-07) described _Aspidonectes nuchalis_ on the
basis of three adults from the Cumberland River and a number of young
from the headwaters of the Tennessee River. Boulenger (1889:245,
footnote 2) suggested that the status of _A. nuchalis_ required
further investigation. The species was not generally recognized after
the turn of the century. Barbour and Loveridge (1929:226) listed MCZ
1908 (one of the juveniles) and 1623-25 as cotypes. Stejneger
(1944:52) showed that _nuchalis_ was not distinguishable from _T. s.
spinifer_, and (_op. cit._:49) listed MCZ 1623-25 as cotypes. Schmidt
(1953:110) restricted the type locality to the Cumberland River, near
Nashville, Tennessee.

Agassiz (_loc. cit._) mentioned that _nuchalis_ "differs strikingly
from Asp. spinifer in the much more elongated form of the male, and in
the great development of the marginal spines and of the tubercles upon
the carapace, ... But the most prominent specific character consists
in the marked depressions on either side of the blunt median keel, and
also in the triangular dilation of that keel behind the front margin
of the carapace." These characters seem to be of no taxonomic worth. I
have seen three syntypes (MCZ 1623-25) that undoubtedly correspond to
the three adult specimens mentioned by Agassiz. All are females,
measuring 19.5, 22.0, and 19.0 centimeters, respectively, in plastral
length, and lack a contrasting mottled pattern on the carapace; the
juvenal pattern is obscured, except for blackish spots at the edge of
the carapace on MCZ 1625, and parts of an ocellus on MCZ 1624. The
dorsal surfaces of the limbs are boldly marked. MCZ 1623, showing the
diagnostic feature mentioned by Agassiz, is photographed by Stejneger
(_op. cit._:Pls. 14, 15), and may be regarded as the lectotype of
_Aspidonectes nuchalis_ Agassiz. MCZ 1908 is one of the young syntypes
mentioned by Agassiz, and is referable to _spinifer_. The juvenal
pattern consists of spots and ocelli; the plastron measures 3.1
centimeters in length, and the carapace 4.2 centimeters.

Wied-Neuwied (1865:55-57, Pl. 5) described the species _?G_[_ymnopus_]
_olivaceus_, but was uncertain whether his interpretation was based on
a species, a variety or a secondary sexual difference. Wied-Neuwied
mentioned that Lesueur had already named this soft-shelled turtle as
_Trionyx ocellatus_, and agreed with Lesueur that those turtles having
occulated spots on the carapace were distinguishable from _T.
spiniferus_ and _T. muticus_. But because Duméril and Bibron in their
_Erpétologie Général_ failed to recognize _T. ocellatus_, Wied-Neuwied
felt obliged to bring it to the attention of his American colleagues
and he renamed it. Wied-Neuwied also stated, in the context of a
synonym, "Beschreibung einer Reise in Nord-America Bd. I., pag. 140."
This comment presumably refers to his earlier description of _T.
annulifer_ (1838:140); seemingly Wied-Neuwied considered _T.
annulifer_ and _G. olivacea_ as conspecific, although there is no
mention of _annulifer_ in the text proper. Stejneger (_op. cit._:49)
designated the type locality of _T. annulifer_ as the Ohio River at
Pittsburgh, Pennsylvania, and of _Gymnopus olivacea_ as New Harmony,
Wabash River, Illinois (_lapsus_ for Indiana).

_Trionyx spiniferus_ was questionably considered distinct from _T.
ferox_ by Lesueur who listed "Testudo ferox Gm. Tortue de Pennant?"
and "Trionyx georgicus Geoffr.?" as synonyms. Subsequently, most
authors considered _T. spiniferus_ synonymous with _T. ferox_ until
Agassiz (1857) pointed out differences between the two species.

The average size of the ocelli on the carapace of the subspecies
_spinifer_ decreases westward toward the Mississippi River; ocelli of
different sizes occur on different individuals from the same state and
presumably from the same population. For example, INHS 2281, plastron
9.9 centimeters in length, from Effingham County, Illinois, has some
ocelli eight millimeters in diameter, whereas a larger male from the
same locality, UI 1322, plastron 11.6 centimeters in length, has the
largest ocelli only five millimeters in diameter. For convenience, all
softshells having locality data from states east of the Mississippi
River are referred to _spinifer_, recognizing that intergradation
occurs with _hartwegi_ over a broad area paralleling the Mississippi
River. The type locality of _spinifer_ is in an area where most
turtles do not have the larger ocelli (diameter of seven to ten mm. on
adult males); however, some individuals from the Wabash River (UMMZ
63523, adult male, plastron 11.5 cm. in length, ocelli diameter seven
mm.) agree with more "typical" _spinifer_ to the east. Intergradation
with _asper_ possibly occurs in that part of the Tennessee River in
eastern Tennessee as exemplified by UMMZ 59198.

Published reports indicate that _T. s. spinifer_ is not abundant in
some of the northeasterly parts of its geographic range. Adams and
Clark (1958:10) wrote that few softshells at Long Point on the
Canadian side of Lake Erie are "ever collected and the area's game
keepers report ... (none) ... seen in recent years. They also tell of
recurrent severe stormy winters in which the muddy bottom of the
marshland was repeatedly churned up and frozen. Such climatic
conditions could easily destroy a large part of the _Trionyx_
population overwintering in the mud bottom." Wright (1919:8) reported
that softshells are "rarely seen" in bays on the New York side of Lake
Ontario, and Babcock (1938:53) wrote that _spinifer_ "is not common in
Lake Champlain."

_T. s. spinifer_ probably extended its geographic range into the
Hudson River drainage of New York _via_ the Erie Canal (connected
Buffalo and Albany) after its completion in the early 1800's (DeKay,
1842:7). Now, the New York Barge Canal (essentially the Erie Canal,
but with minor changes in course and the addition of several spurs)
provides an avenue for dispersal of _spinifer_ to the Hudson River
drainage, Lake Ontario and intervening waterways in New York (Mertens,
1928:199). Netting (1944:86-87), however, suggested that _spinifer_
occupied Lake Champlain, the Finger Lakes, Mohawk River and upper
Hudson in the late stages of the formation of the Great Lakes.

A publication not seen by me is that of Mansueti and Wallace (1960).
Its title suggests that _Trionyx_ occurs in Maryland.

The unsuccessful introduction of _T. s. spinifer_ in the Delaware
drainage in New Jersey has been discussed by Fowler (1907:213), who
wrote that they were found as early as the late 1860's and were
introduced when young presumably to stock aquaria. Records of
occurrence include Cooper's Creek, Camden County (Stone, 1906:168);
Woodbury, Gloucester County (Cope, 1894:889); and Paulins Kill at
Hainesburg, Warren County (Johnson, 1894:889).

Surface (1908:122) believed that soft-shelled turtles "have doubtless
been introduced into the eastern part of Pennsylvania through the
canal from the Western and Central part of New York," and Roddy (_in_
Neill, 1951:21) suggested that the species may be found in the
Susquehanna River. Babcock (1919:420) mentioned a young specimen of
_spinifer_ in the collection of the Boston Society of Natural History
that was obtained "in White River, Vermont," a tributary of the
Connecticut River of the Atlantic Coast drainage; seemingly this
record has not been accepted and the species is not established. To my
knowledge, populations of _T. s. spinifer_ do not occur in rivers of
the Atlantic Coast drainage, except probably the Hudson-Mohawk
drainage.

Stockwell (1878:401) wrote that _spinifer_ was found "as high as
Athabasca." Presumably Stockwell referred to Lake Athabaska in
northern Alberta and Saskatchewan, Canada, a region where soft-shelled
turtles are unknown; see also the comments by Stejneger (1944:52).

_Specimens examined._--Total 250 as follows: ALABAMA: _Morgan_: UMMZ
99578, "near" Decatur.

ILLINOIS: _Adams_: INHS 2150, Quincy. _Bond_: INHS 8345, Greenville.
_Carroll_: CNHM 42116, Ordnance School Proving Ground. _Cass_: INHS
2151, Beardstown. _Champaign_: INHS 2273, 2311, 2413, 3142, "near"
Seymour; INHS 4229, Champaign; INHS 6163, Sidney. _Christian_: INHS
1560, Pana. _Coles_: INHS 1968-69, 2 mi. W Charleston. _Cumberland_:
INHS 2282, Greenup. _De Witt_: INHS 7674, Farmer City. _Effingham_: UI
1322, 2281, 19365, "near" Effingham. _Fulton_: INHS 5531, 2 mi. NE
Bluff City, Schyler County; UI 23449, Liverpool; UI 24611, Spoon
River, 18 mi. NW Canton. _Hancock_: USNM 53522, 59277, "near"
Hamilton. _Iroquois_: INHS 6869-70, 2.5 mi. N Crescent City.
_Jackson_: TU 1369 (12), Elkville. _Kane_: CNHM 42400, Aurora.
_Kankakee_: CNHM 324, Momence. _Kendall_: UI 2411, Plano. _Logan_:
INHS 7171-72, 6 mi. N Lincoln. _Madison_: USNM 60571. _Macoupin_: UI
2401-02, Beaver Dam Lake. _Mason_: CNHM 346, 470, INHS 1122, 1559,
5756-58, UI 42, 2404, Havana, Lake Chautauqua. _Mercer_: CNHM 3220,
New Boston. _Morgan_: CNHM 2067 (2), 3290, 3303-04, 3306, INHS 2152,
2154, 5132-37, USNM 54747, Meredosia. _Moultrie_: INHS 8989, 2 mi. NW
Lovington. _Peoria_: UI 2406-10, Peoria. _Pope_: INHS 5505, Lake
Glendale. _Putnam_: UMMZ 81604-14, 5 mi. N Henry, Marshall County.
_Schuyler_: UI 2405, "near" Ripley, Brown County. _Scott_: INHS 2149,
2153, Naples. _Union_: CNHM 18623, 6 mi. SW Jonesboro. _Vermilion_:
INHS 3142, Muncie; INHS (1 untagged); UI 1970, 3209, Danville; UI
2403, 1.5 mi. E Oakwood; UI 16265, Kickapoo State Park. _Wabash_: USNM
12061, Mt. Carmel. _Winnebago_: INHS 7185, Kishwaukee Forest Preserve;
INHS 7294, 1/2 mi. S Shirland. _County unknown_: USNM 7661.

INDIANA: _Bartholomew_: UMMZ 61060, 10 mi. W Columbus. _Carroll_: USNM
42905-06, Burlington. _Clark_: UMMZ 110599, 14-mile Creek, 3 mi. NW
Charleston. _Decatur_: UMMZ 55416, 3 mi. S Westport. _Elkhart_: UMMZ
105598, Elkhart River, south of Goshen. _Gibson_: UMMZ 89744, Foot's
Pond. _Johnson_: UMMZ 108062, 2 mi. S Trafalgar. _Knox_: USNM 22711,
Vincennes. _Kosciusko_: AMNH 8379, UMMZ 84287 (5), Winona Lake; UMMZ
110235, Wawasee Lake. _Lake_: CNHM 11019, 11021-24, Crown Point.
_Marion_: UMMZ 103393, Ravenswood; UMMZ 110236, 1 mi. N Lawrence.
_Marshall_: CNHM 39299; USNM 33495, Yellow River north of Burr Oak;
USNM 33496-501, 35404, 42583-84, Lake Maxinkuckee. _Wells_: UMMZ
63523, Wabash River, Bluffton. _County unknown_ (Lagrange or
Marshall): USNM 50670, Twin Lakes.

KENTUCKY: _Casey_: UMMZ 112252, trib. of Green River, south of
Yosemite. _Green_: UMMZ 116718, Little Barren River, 1.5 mi. E Monroe,
Hart County. _Rockcastle_: UMMZ 98767, Rockcastle River, 5 mi. above
Livingston.

MICHIGAN: _Allegan_: UMMZ 42112, Kalamazoo River. _Barry_: UMMZ 53874,
Thornapple River, 3 mi. NW Hastings. _Bay_: UMMZ 74670. _Branch_: UMMZ
95615, 1 mi. S Kinderhook; UMMZ 70748, Hog Creek. _Calhoun_: UMMZ
89950 (3); UMMZ 79133, near Battle Creek. _Cass_: UMMZ 40866-67,
53005, Diamond Lake; UMMZ 40868, 52948, Long Lake. _Jackson_: UMMZ
72494. _Kalamazoo_: UMMZ 42130, 80534, Kalamazoo; UMMZ 90506, Gull
Lake; UMMZ 92599, Kellogg Bird Sanctuary. _Lenawee_: UMMZ 72457,
Devil's Lake; UMMZ 74662, Wolf Lake Park. _Livingston_: UMMZ 54401,
76190, Portage Lake. _Monroe_: UMMZ 44604-06, USNM 51213, "near"
Monroe. _Newaygo_: UMMZ 63469. _Oakland_: UMMZ 64363, Hay's Creek;
UMMZ 96539, Clinton River. _Ottawa_: UMMZ 81699. _St. Joseph_: UMMZ
38876, 38889, "near" White Pigeon; UMMZ 96537, Corey Lake. _Van
Buren_: UMMZ 90003, Wolf River, west of Kalamazoo, Kalamazoo County.
_Washtenaw_: SM 2035, 2038, 2105, UMMZ 39847, 96538, "near" Ann Arbor;
UMMZ 35765, 35769, 74518 (2), Portage Lake; UMMZ 54402-03, Little
Lake; UMMZ 89659, Huron River, Dexter; UMMZ 110583-85. _County
unknown_ (Washtenaw or Livingston): UMMZ 54400, Huron River near
Portage Lake.

MISSISSIPPI: _Adams_: MCZ 46615, UMMZ 76446, "near" Natchez; MCZ
46621, 46633, USNM 01084, 01086, Washington. _Coahoma_: AMNH 5289,
5285-86, Moon Lake. _Lafayette_: MCZ 37173, Oxford; USNM 7650,
Abbeville? (reported from Abbeville, South Carolina by Pickens,
1927:113; see discussion by Stejneger, 1944:50, and my comments on
page 509 beyond). _LeFlore_: USNM 73668-69, Greenwood. _Madison_: USNM
95192, Big Black River. _Washington_: USNM 115980, Deer Creek.
_Yazoo_: UMMZ 86669, Panther Creek west of Yazoo City; UMMZ 83304,
Yazoo City.

NEW YORK: _Monroe_: CNHM 92001-02, Genesee River, Rochester. _Wayne_:
AMNH 69931, CNHM 92004, Sodus Bay.

OHIO: _Athens_: UMMZ 111793, east branch Shade Creek. _Franklin_: USNM
26290. _Lucas_: USNM 51214, Toledo. _Pike_: UMMZ 99309, Morgan's Fork,
Sunfish Creek. _Warren_: AMNH 4763, Little Miami River, 3 mi. below
Morrow. _County unknown_: USNM 21128-29, Cuyahoga River.

TENNESSEE: _Benton_: UMMZ 113036, Eagle Creek, 1/2 mi. E Holliday.
_Bradley_: UMMZ 59197, west branch of Chestnee Creek, 7 mi. E
Cleveland. _Claiborne_: USNM 86677, 5 mi. SE Cumberland Gap, Powell
River. _Davidson_: MCZ 1623-25, Cumberland River near Nashville
(restricted locality); USNM 7165-67, Nashville. _Decatur_: KU 3000,
Perryville. _Hamilton_: USNM 131861, Chattanooga. _Monroe_: TU 16058,
Little Tennessee River, 10 mi. N Madisonville. _Obion_: UMMZ 53199,
USNM 102911, Reelfoot Lake. _Overton_: UMMZ 69561 (2), Wirmingham.
_Sevier_: TU 16132, UMMZ 86735, USNM 86681-82, near Sevierville; UMMZ
86734, Walden Creek "near" Gatlinburg. _County unknown_: MCZ 1908,
headwaters of Tennessee River.

VIRGINIA: _Smythe_: USNM 101386, Holston River, Seven Mile Ford.

WEST VIRGINIA: _McDowell_: USNM 33767, Dry Fork, Perryville (county
questionable, perhaps Randolph County).

WISCONSIN: _Chippewa_: CNHM 8223, Lake Wissota, mouth of Yellow River,
Anson Twp. _Polk_: UMMZ 72511-12, St. Croix River "near" Never's Dam.
_County unknown_: CNHM 15971, Eau Claire River.

_Records in the literature._--ONTARIO: _Carleton_: Ottawa
(questionable record). _Essex_: Point Pelee. _Haldimand_: Dunville.
_Kent_: Lake St. Clair. _Norfolk_: Long Point. _Oxford_: Beachville.
_Wentworth_: Hamilton Bay (Logier and Toner, 1955:51).

QUEBEC: _Iberville_: Richelieu River at Iberville (Logier and Toner,
1955:51).

ALABAMA: _Lawrence_: Courtland (Stejneger, 1944:53).

ILLINOIS: _Boone_: Belvidere. _Bureau_: Bureau. _Cass_: Chandlerville.
_Clay_: Louisville (Cahn, 1937:189). _Cook_: Lake Michigan (Kennicott
_in_ Stejneger, 1944:44); Evanston (Necker, 1939:10); Chicago (Schmidt
and Necker, 1935:76). _Crawford_: Robinson. _Douglas_: northern part
of county (P. W. Smith, 1947:39). _Fayette_: Vandalia. _Fulton_:
Ellisville (Cahn, _loc. cit._). _Grundy_: Morris (Stille and Edgren,
1948:201). _Jackson_: Jacob (Cagle, 1942:158). _Jersey_: Grafton
(Cahn, _loc. cit._). _Kane_: Batavia; Dundee Game Farm (Stille and
Edgren, _loc. cit._). _Kankakee_: Kankakee River near Altort (Necker,
_loc. cit._). _Lake_: Fox Lake. _LaSalle_: Streator (Cahn, _loc.
cit._). _Lawrence_: (Hahn _in_ Stejneger, 1944:44). _Lee_: symbol on
map (Cahn, _loc. cit._). _McHenry_: McHenry (Stille and Edgren, _loc.
cit._). _Macon_: Decatur. _Macoupin_: Carlinville (Cahn, _loc. cit._).
_Ogle_: Oregon (Garman _in_ Cahn, _loc. cit._). _Randolph_: Chester,
Reily Lake. _Rock Island_: Barstow, Hillsdale, Rock Island (Cahn,
_loc. cit._). _Saline_: Horseshoe Lake (Stein, 1954:312).
_Stephenson_: Freeport (Cahn, _loc. cit._). _Union_: Bluff Lake
(Garman _in_ Cahn, _loc. cit._). _Whiteside_: Sterling, symbol on map
(Cahn, _loc. cit._). _Williamson_: Marion (Cagle, 1942:158).
_Winnebago_: Rockton; symbol in western part of county (Cahn, _loc.
cit._). _County unknown_: Fox River (Yarrow, 1882:29).

INDIANA: _Brown_: 1 mi. below Helmsburg (Myers, 1927:339). _Clay_: Eel
River (Kirsch _in_ Stejneger, 1944:45). _Franklin_: (Hughes _in_
Stejneger, _loc. cit._). _Jasper_: Jasper-Pulaski Game Preserve
(Swanson, 1939:690). _Jefferson_: Madison (Myers, _loc. cit._).
_Marion_: Irvington (Stejneger, _op. cit._:55). _Marshall_: 2 mi. NW
Culver (KKA). _Monroe_: Bloomington (McLain _in_ Stejneger, _op.
cit._:45). _Newton_: Lake Village (Stille and Edgren, _loc. cit._).
_Posey_: Wabash River at New Harmony (Lesueur, 1827:257). _Starke_:
Grant (Stille and Edgren, _loc. cit._). _Steuben_: Fish Creek "near"
Hamilton (Stejneger, _op. cit._:53). _County unknown_ (Knox or
Starke): USNM 72387, Knox (Stejneger, _op. cit._:55); "White Water
valley," east-central part of state (Butler, 1894:224). USNM 8359 (=
_Trionyx spinifer asper_) has been erroneously recorded from Madison,
Indiana, by Yarrow (1882:29) and Hay (1892:145); see discussion by
Cahn (1937:200) and Stejneger, (_op. cit._:73, 75).

KENTUCKY: _Edmonson_: Green River, Mammoth Cave National Park
(Hibbard, 1936:281). _Fleming_: Fox Creek (Welter and Carr, 1939:130).
_Jefferson_: (Funkhouser, 1925:71). _Morgan_: (Stejneger, 1944:54).
_County unknown_: Ohio and Pond rivers (Funkhouser, _loc. cit._).

MICHIGAN: _Berrien_: mouth of St. Joseph River at St. Joseph (Lagler,
1943:303). _Eaton_: Brookfield; Olivet (Clark _in_ Ruthven, Thompson
and Thompson, 1912:133). _Genesee_: (Miles _in_ Ruthven, Thompson and
Thompson, _loc. cit._). _Iosco_: (Lagler, 1943:283, symbol on map).
_Kent_: (Lagler, _loc. cit._). _Montcalm_: (Clark _in_ Ruthven,
Thompson and Thompson, _loc. cit._). _Muskegon_: Muskegon River "near"
Muskegon (Lagler, _op. cit._:303). _Van Buren_: Reynolds Lake, 2.5 mi.
E Lawrence (Edgren, 1942:180).

MISSISSIPPI: _De Soto_: Lake Cormorant (Stejneger, 1944:55). _Holmes_:
Thornton (Cook, 1946:185). _Humphreys_: Belzoni (Stejneger, _loc.
cit._). _Sunflower_: _Warren_: Vicksburg, Eagle Lake (Cook, _loc.
cit._). _Washington_: Lake Washington (Smith and List, 1955:125);
Greenville (Stejneger, _loc. cit._).

NEW YORK: _Albany_: Hudson River at Albany (DeKay, 1842:7); Mohawk
River at Cohoes (Eights _in_ Bishop, 1923:120). _Cattaraugus_:
Allegheny River and Red House Lake in Allegheny State Park (Eaton,
1945:115). _Chautauqua_: Lake Chautauqua (DeKay, _loc. cit._).
_Monroe_: Braddocks Bay and Long Pond on Lake Ontario (Wright,
1919:8). _Saratoga_: Hudson River near Baker's Falls (restricted
locality, Rafinesque, 1832:64). _County unknown_: Lake Cayuga; Mohawk
River (DeKay, _loc. cit._).

OHIO (Conant, 1951:158-59, 264, except records from Allen, Geauga and
Noble counties): _Allen_: Sugar Creek, 6 mi. N Lima (Adler and Dennis,
1960:27). _Ashland_: Long Lake, Lake Twp.; Black Fork, Sec. 27, Green
Twp. _Athens_: Hocking River "near" Athens; "near" Fisher, Alexander
Twp. _Auglaize_: Pusheta Creek, west of Wapakoneta. _Brown_: White Oak
Creek, 1 mi. N Higginsport. _Butler_: Oxford. _Champaign_: Mad River,
4 mi. SW Urbana. _Coshocton_: Walhouding River, below dam. _Defiance_:
Auglaize River, Shawnee Scout Camp, Defiance Twp. _Erie_: Huron;
Sandusky. _Fairfield_: Buckeye Lake. _Franklin_: Alum Creek,
Westerville; Columbus. _Geauga_: Chardon Twp. (Wood, 1959:8).
_Greene_: Huffman Dam. _Hamilton_: Harrison; mouth of Miami River.
_Hardin_: "near" Hepburn. _Henry_: Maumee River, east of Napoleon;
Maumee River "near" Texas; Maumee River, 3 mi. W Texas. _Highland_:
Little Brush Creek, 2 mi. N Sinking Spring. _Huron_: Huron River
"near" Monroeville. _Jackson_: Canter's Cove, Jackson Twp.; Jackson
Lake. _Knox_: Brinkhaven. _Lake_: east branch Chagrin River, Kirtland;
Grand River, 4 mi. E Painesville. _Lawrence_: Pine Creek, Elizabeth
Twp. _Logan_: Miami River, "near" Indian Lake. _Lorain_: Oberlin.
_Lucas_: Lake Erie at Reno Beach, Jerusalem Twp.; Lake Erie, 1/2 mi.
offshore from mouth of Crane Creek; Maumee River at Maumee; Swan
Creek, W of Toledo; "near" Waterville; Swan Creek "near" Whitehorse.
_Madison_: London. _Medina_: Hinckley Lake. _Meigs_: Shade River,
below Darwin. _Miami_: Miami River, above Troy. _Monroe_: Cranenest
Fork, Green Twp. _Montgomery_: Mad River, Dayton; Miami River, Dayton;
Stillwater River, Dayton. _Morrow_: Kokosing River, Franklin Twp.
_Noble_: Jct. Sharon Twp. 1 and St. Rt. 78. (Adler and Dennis,
1960:27). _Ottawa_: East Harbour, Catawba Island. _Pike_: Chenoweth
Fork, Sunfish Twp.; Scioto River, Camp Creek Twp. _Ross_: Paint Creek
near Bainbridge. _Vinton_: Lake Hope; Lake Alma. _Warren_: Fort
Ancient. _Washington_: Dam No. 2, Muskingum River, "near" Marietta.
_Williams_: 1 mi. S Blakesley; St. Joseph River "near" Blakesley; West
Branch, St. Joseph River, Sec. 8, Bridgewater Twp.; Edgerton. _Wood_:
Grand Rapids; Grassy Creek, Rossford; Haskins; Maumee River opposite
Toledo.

PENNSYLVANIA: _Allegheny_: Monongahela River above McKeesport
(Atkinson, 1901:154); Ohio River at Pittsburgh (Wied-Neuwied _in_
Stejneger, 1944:44, 49). _Armstrong_: (Swanson, 1952:165). _Clarion_:
Clarion River "near" Clarion (Allen, 1955:228); Foxburg (= Foxbury?,
Boulenger, 1889:260). _Crawford_: _Elk_: _Erie_: Edinboro Lake.
_Forest_: (Swanson, _loc. cit._). _Indiana_: Plum Creek; Crooked Creek
(Netting _in_ Stejneger, 1944:48). _McKean_: (Swanson, _loc. cit._).
_Somerset_: Stoyestown (Surface, 1908:122). _Warren_: _Venango_:
Allegheny River south of Franklin (Swanson, _loc. cit._).

TENNESSEE: _Chester_: South Fork, Forked Deer River just E Henderson
(Endsley, 1954:40). _Clay_: Mill Creek, 3 mi. from Butler's Landing;
Obey River above mouth of Wolf River at Lilydale; mouth of Wolf River
(Shoup, Peyton and Gentry, 1941:75); Iron Creek "near" Willow Grove
(Stejneger, 1944:56). _Fentress_: _Jackson_: (Gentry, 1941:332).
_Lake_: Reelfoot Lake (Parker, 1948:29). _Obion_: Walnut Log (Parker,
1937:85); east shore of Reelfoot Lake, Samburg (Rhoads, 1895:386).
_Overton_: Medlock Branch, tributary of West Fork Obey River north of
Allred (Shoup, Peyton and Gentry, _loc. cit._). _Roane_: 2 mi. S
Kingston (Stejneger, 1944:55).

VERMONT: _Chittenden_: Lake Champlain, mouth of Winooski River; "near"
Burlington; Milton (= Minton) (Babcock, 1919:420). _Franklin_: Swanton
(Stejneger, 1944:55).

WEST VIRGINIA: _Randolph_: Tygart River at Elkins (Green, 1937:116).

WISCONSIN: _Burnett_: _Crawford_: (Pope and Dickinson, 1928:83).
_Dane_: Lake Wingra, Madison (Noland, 1951:54). _Grant_: (Pope and
Dickinson, _loc. cit._). _Green Lake_: Berlin (AMNH 6840-41, listed in
card file March 2, 1959). _Jefferson_: Lake Mills (Dickinson,
1950:75). _La Crosse_: West Salem (Pope, 1930:281). _Oneida_: _Pepin_:
(Pope and Dickinson, _loc. cit._). _Racine_: Eagle Lake (Edgren,
1944:498); Burlington; Rochester (Stille and Edgren, 1948:201).
_Sheboygan_: Sheboygan (KKA). _Trempealeau_: _Vernon_: "near" Viroqua
(Pope, _loc. cit._). _Walworth_: Lake Beulah (Dickinson, _loc. cit._).
_Washburn_: (Pope and Dickinson, _loc. cit._). _Waukesha_: Lac La
Belle (Cahn, 1929:8). _Winnebago_: Wolfe River (Dickinson, _loc.
cit._).

=Trionyx spinifer hartwegi= (Conant and Goin)

Western Spiny Softshell

Plates 35 and 36

_Amyda spinifera hartwegi_ Conant and Goin, Occas. Papers Mus.
Zool. Univ. Mich., No. 510:1, pl. 1, map 1, June 15, 1948.

_T[rionyx] s[pinifer] hartwegi_ Schwartz, Charleston Mus. Leaflet,
No. 26:11, May, 1956.

_Type._--Holotype, UMMZ 95365; alcoholic adult male; obtained at
Wichita, Sedgwick County, Kansas, in May, 1945, by Robert Young.

_Range._--Central United States in tributaries flowing into the
Mississippi River from the west, except the Red River drainage;
eastern Montana, North Dakota, and southern Minnesota south to eastern
Colorado, northern Oklahoma and Arkansas (see map, Fig. 19).

_Diagnosis._--Juvenal pattern of small ocelli, rarely as large as two
millimeters in diameter, or usually solid black dots that are not
much larger in center of carapace than at sides (mean OD/PL, Kansas,
.022); only one dark marginal line separating pale rim of carapace
from dorsal ground color.

_Description._--Plastral length of smallest hatchling, 2.8 centimeters
(USNM 9928); of largest male, 13.1 centimeters (USNM 55687); of
largest female, 25.5 centimeters (KU 2283).

Carapace olive, having small ocelli or black spots that are not much
larger in the center of the carapace than at the sides; pale rim of
carapace separated from darker ground color by one dark marginal line
and not four or five times wider posteriorly than laterally; large
females often having black dots at sides of carapace on mottled and
blotched pattern; pattern on snout of pale, dark-bordered stripes that
unite forming acute angle in front of eyes; well-defined dark markings
in subocular and postlabial region; pattern contrasting with ground
color on side of head; postlabial stripe broken, interrupted; pale
postocular stripe having blackish borders interrupted, not joining
with postlabial stripes; dorsal surface of soft parts of body having
contrasting pattern, largest blackish marks on hind limbs; elongate
tail of males having pale dorsolateral bands with well-defined, lower,
blackish borders; patterns on soft parts of body usually obscured or
absent on large females; underparts whitish, often having blackish
marks, except in center of plastral area; dark marks on webbing of
limbs, palms and soles; dark streaks often coincident with digits;
tubercles along anterior edge of carapace small and conical on adult
males, and conical or knoblike on large females; accessory, knoblike
tubercles in nuchal region and in middle of carapace posteriorly on
large females.

Ontogenetic variation in PL/HW, mean PL/HW of specimens having
plastral lengths 7.0 centimeters or less, 4.24, and exceeding 7.0
centimeters, 5.33; ontogenetic variation in CL/CW, mean CL/CW of
specimens having plastral lengths 8.5 centimeters or less, 1.12, and
exceeding 8.5 centimeters, 1.19; mean CL/PCW, 2.00; mean SL/HW, 1.30
(including subspecies _spinifer_); mean CL/PL, 1.38.

_Variation._--Variants include: CNHM 8949, UMMZ 72511 and TU 14591
having ocelli approximately 4 millimeters in diameter that are almost
solid spots; KU 17728 having pale stripes on snout that lack black,
inner borders; TTC 719 (female, plastral length 20.7 cm.), having
distinct pattern on snout; USNM 14535, 17823, 55684, and 123446 (from
different localities) having markings confined to margins of carapace
(Stejneger, 1944:66, suggested that USNM 17823 probably came from
Texas); UMMZ 92667 (female, plastral length 6.7 cm.) lacking pattern
on carapace.

_Comparisons._--_T. s. hartwegi_ can be distinguished from all other
subspecies of _T. spinifer_ by the presence of small dots and ocelli
on the carapace that are all of approximately the same size in
combination with only one dark marginal line. _T. s. hartwegi_
resembles _asper_ in having small blackish ocelli or dots on the
carapace but differs from _asper_ in having only one dark marginal
line. _T. s. hartwegi_ differs from _spinifer_ only in the small size
of the ocelli. _T. s. hartwegi_ resembles _spinifer_ and _asper_, but
differs from _pallidus_, _guadalupensis_ and _emoryi_ in having
blackish spots and ocelli on the carapace and lacking small whitish
spots. _T. s. hartwegi_ resembles _spinifer_, _asper_ and _pallidus_
but differs from _guadalupensis_ and _emoryi_ in having conical or
knoblike tubercles on the anterior edge of the carapace on large
females.

_T. s. hartwegi_ differs from the subspecies _asper_, _guadalupensis_
and _emoryi_ in having a narrower head, and from _emoryi_ in having a
wider carapace. _T. s. hartwegi_ resembles _spinifer_ and _asper_ but
differs from the other subspecies in having the carapace widest at a
plane approximately one-half way back on the carapace. _T. s.
hartwegi_ and _spinifer_ have longer snouts than do _pallidus_ and
_guadalupensis_ or _emoryi_. _T. s. hartwegi_ differs from _asper_ but
resembles the other subspecies in having a relatively longer plastron.

_Remarks._--The validity of _T. s. hartwegi_ has never been
questioned. It intergrades with _spinifer_ over a broad area
paralleling the Mississippi River. For convenience, specimens
occurring west of the Mississippi River are referred to the subspecies
_hartwegi_. Figure 8 shows much variation in size of ocelli on
different individuals from the same state. For example, UMMZ 92667,
plastral length 6.7 centimeters has a uniform pale brown carapace
lacking any dark marks, whereas UMMZ 92652, plastral length 5.9
centimeters has some ocelli three millimeters in diameter on the
carapace. Both are from Iowa. One specimen from Kansas, KU 1954
(Doniphan County, plastral length 11.8 cm.), has ocelli four
millimeters in diameter, and USNM 7648 captured farther west at Fort
Laramie, Wyoming, an adult male having a plastral length of 11.0
centimeters, has some ocelli five millimeters in diameter on the
carapace. TTC 1090, an adult male from the panhandle of Texas has some
ocelli so much as 5.5 millimeters in diameter. The size of the ocelli
seemingly varies in the same local population.

Specimens of _T. spinifer_ in the lower Mississippi Valley are
intergrades. Most individuals have small black dots on the carapace;
some have small ocelli (TU 7216, 7501, 11912, 12123-24) interspersed
with black dots (TU 5863), others have black dots confined to the edge
of the carapace (TU 157, 4539, 7105), and still others have no pattern
on the carapace (TU 7506, 13698.1, 10087.6). Two large males (TU
11580, 13025) have large ocelli (approximately five mm. in diameter)
that have nearly black centers. In general, there is more dark
pigmentation than farther north; some specimens have extensive
pigmentation on the ventral surface of the carapace and soft parts of
the body (TU 156, 5648). The dorsal surface of the limbs, especially
the hind limbs, have a bold, black marbling and may be almost
completely black (TU 5484, 5597). Many females, not exceeding plastral
lengths of 7.0 centimeters, have a pale blotched pattern of lichenlike
figures or have ill-defined black dots on the carapace (TU 10087,
13698.13, 13753.15).

Localities of specimens of _T. spinifer_ occurring in the Mississippi
River drainage in Mississippi are arbitrarily listed under the account
of the subspecies _spinifer_, whereas those in Louisiana (excluding
_pallidus_) are listed under the account of _hartwegi_.

Neither Over (1943) nor Wheeler (1947:169) record _T. s. hartwegi_,
respectively, from South Dakota or North Dakota; records from the
Missouri River drainage in Montana suggest the occurrence of the
species in that drainage in North and South Dakota.

_Specimens examined._--Total, 392 as follows: ARKANSAS: _Clay_: UMMZ
70735 (2), 7 mi. S St. Francis. _Crawford_: USNM 95352, Lee Creek, 7
mi. NW Natural Dam. _Drew_: CNHM 40785. _Lafayette_: KU 2225-29, 2944
(one of three specimens bearing last catalog number), 2963 (one of
three specimens bearing this catalog number), 2964 (one of two
specimens bearing this catalog number), Lewisville (see remarks under
the account of the subspecies _pallidus_). _Lawrence_: CNHM 8949;
CNHM 12598-600, 12602-04, TU 5855, UI 2413, Imboden; UI 2412, Black
River at Powhatan. _Marion_: TU 14591 (6), White River at Cotter.
_Prairie_: KU 1867, 1869, 1879, 1949-51, 2280-83, 2285-91 (2 specimens
bear catalog number 2287), 2307, 2761-62, 2666, 2826, 2842, 3346-47,
White River at DeValls Bluff. _Pulaski_: UMMZ 96540, Little Rock.
_Saline_: USNM 17823, Saline River at Benton. _Searcy_: UMMZ 92755,
Little Red River, 1.5 mi. SE Leslie. _Yell_: TU 14565, Petit Jean
Creek, 10 mi. N Casa. _County unknown_: CNHM 28566-67, Ouachita River.

IOWA: _Allamakee_: UMMZ 72556-58, 92642-49, Mississippi River "near"
Lansing. _Appanoose_: UMMZ 92667, Chariton River, 4.3 mi. N.
Centerville. _Decatur_: UMMZ 92651, Grand River, 3.5 mi. WSW Decatur.
_Dickinson_: UMMZ 55249, Milford; UMMZ 92655, Spirit Lake Twp.
_Hamilton_: USNM 9928, Webster City. _Hardin_: UMMZ 92650, Eldora.
_Louisa_: UMMZ 92654, Muscatine Slough, 12 mi. SW Muscatine, Muscatine
County. _Muscatine_: INHS 7675, 5.5 mi. SE Muscatine; USNM 54730-32,
Fairport. _Scott_: CNHM 433, Davenport; UMMZ 92656, Steamboat Slough,
2 mi. N Princeton. _Story_: UMMZ 92653, Squaw Creek at Ames.
_Washington_: UMMZ 92652, English River, 2 mi. E Riverside.

KANSAS: _Anderson_: KU 52286-87, 3-1/4 mi. E, 1/2 mi. N Colony.
_Atchison_: UMMZ 66939-41, Atchison. _Barber_: KU 17728, 4.5 mi. S Sun
City; KU 41379, 41742, 6 mi. N, 3.5 mi. E Sharon; USNM 100580,
Medicine River, 1 mi. S Lake City. _Cherokee_: KU 1323, Galena.
_Comanche_: KU 18385, 3-4 mi. SE Arrington. _Cowley_: UMMZ 75963, USNM
90441-44, 91022, 100529-30, "near" Winfield. _Doniphan_: KU 1943,
1952-54, Doniphan Lake. _Douglas_: KU 1955-56, Wakarusa River; KU
40176-77, Kansas River at Lawrence. _Franklin_: KU 3290. _Hamilton_:
KU 2990, Syracuse. _Harper_: KU 18159, 1 mi. N Harper. _Kingman_: USNM
95261, 2 mi. E Calista. _Labette_: KU 3339. _Lane_: KU 3738-41,
Pendennis. _Logan_: KU 16531, Smoky Hill River, 3 mi. SW Elkader.
_Meade_: KU 40210, Crooked Creek, 12.5 mi. S, 1-1/4 mi. W Meade.
_Montgomery_: KU 3731-32, Independence; KU 50856, Cherryvale Lake.
_Neosho_: UMMZ 69294, Caneville Creek, 32 mi. N. Parsons, Labette
County. _Osage_: KU 3294-96, Appanoose Creek. _Pratt_: KU 15931-32,
15934, State Fish Hatchery "near" Pratt. _Riley_: KU 48239, McDowell
Creek, WSW Manhattan; UMMZ 64434, "near" Manhattan. _Russell_: KU
3289. _Sedgwick_: UMMZ 95363-65, Wichita. _Shawnee_: USNM 123446,
Kansas River at Topeka. _Stafford_: KU 3758, Little Salt Marsh; KU
41743, 13.5 mi. N, 6 mi. E Stafford. _Trego_: KU 2757, 3769, Smoky
Hill River, 10 mi. N (NNE) Utica, Ness County; KU 51517, Saline River,
5 mi. N, 1/2 mi. E Wakeeney. _Wilson_: KU 56744-45, Verdigris River, 1
mi. S Altoona. _Woodson_: KU 55295, Neosho River, 1/2 mi. E, 1-1/2 mi.
S Neosho Falls. _County unknown_: USNM 51529.

LOUISIANA: _Catahoula_: TU 12629, Ouachita River, 4 mi. N
Harrisonburg. _Claiborne_: TU 13080, Caney Lake "near" Summerfield.
_Concordia_: KU 50849, Tensas River at Clayton; TU 16524 (3), USNM
012349, Lake Concordia; USNM 99865, Red River "near" Shaw. _East
Carrol_: TU 827-30, 905, 5644-45, Lake Providence. _Grant_: TU 12735,
Big Creek at Fishville, "near" Pollock. _Jefferson_: TU 5592-98, 7184,
10741, 10171, Mahogany Pond. _Lafourche_: TU 7105, 7132, 7216, 7501,
7505-07, 10087 (14), 11828-29, 11912, 11983 (2), 12123-28, 13502,
13679 (8), 13753 (22), 13766.2, Bayou Lafourche at Raceland.
_Morehouse_: USNM 11631 (2), Mer Rouge. _Natchitoches_: USNM 100420,
Cane River "near" Natchitoches. _Orleans_: TU 16169 (3), Audubon Park,
New Orleans; USNM 029310, "near" New Orleans. _Ouachita_: TU 12916,
12954, 12970-71, 13019, 13025, Bartholomew Bayou at Sterlington; TU
5988, Monroe. _Pointe Coupee_: TU 153, 156-59, 165, 5484, 5513,
5518-19, 5646, 5648, 5651, USNM 100202-12, False River at New Roads.
_Rapides_: TU 14040, Red River at Rapides. _Richland_: OU 25082. _St.
Bernard_: TU 16170, Delacroix Island. _St. Charles_: TU 4539, 4579,
5224, 5990, 11928 (12), 13698 (16), Bayou Gauche between Paradis and
Des Allemands; TU 5863, 11580, Bonnet Carre Spillway at Norco.
_Tensas_: TU 5762, Lake St. Joseph near Newellton. _Union_: USNM
138946, Meridian Creek, 1 mi. E Conway; USNM 138947, Ouachita River,
Alabama Landing. _Parish unknown_: MCZ 1622, Lake St. John (Concordia
or Tensas Parish); USNM 029266, Louisiana?

MINNESOTA: _Hennepin_: AMNH 4759-60, Fort Snelling. _Lesueur_: KU
46742-43, Waterville, Lake Tetonka. _Winona_: USNM 59263-66, Homer.

MISSOURI: _Carter_: UMMZ 70737, "near" Van Buren. _Chariton_: UI
17509, Triplett. _Franklin_: USNM 55689. _Gasconade_: UMMZ 95900,
Bourbeuse Creek, 8 mi. S Owensville. _Jefferson_: USNM 95405, Glaize
Creek. _Lewis_: USNM 59279-80, Canton. _Miller_: UMMZ 91929, Barren
Fork Tavern Creek, 5 mi. NW Iowna. _Newton_: UMMZ 82822, Shoal Creek,
12 mi. W Momit. _Phelps_: UMMZ 91930, Bourbeuse River, 10 mi. N St.
James. _Reynolds_: CNHM 35392, Black River at Warner Bay Spring; USNM
55688. _Ripley_: UMMZ 90435. _Shannon_: INHS 6223, Alley Spring State
Park. _St. Charles_: USNM 93089-94, Dardenne Creek, St. Peters. _St.
Louis_: USNM 55685-87, Mississippi River at St. Louis. _Stone_: USNM
55684. _Washington_: USNM 55690. _Wayne_: UI 16554, Sam A. Baker State
Park; UMMZ 95879, St. Francis River at Lodi. _County unknown_ (Wayne
or Butler): UMMZ 83264, Clark National Forest, St. Francis River.

MONTANA: _Big Horn_: USNM 54421, Crow Agency. _Roosevelt_: USNM 58,
Fort Union (locality reads "Yellowstone, Fort Union"; probably the
Yellowstone River near Fort Union). _Wheatland_: UMMZ 92005,
Musselshell River near Shawmut. _Yellowstone_: USNM 14535, Custer.

OKLAHOMA: _Alfalfa_: OU 9316, 2 mi. S Cherokee. _Cleveland_: OU 22973,
Norman. _Delaware_: UMMZ 81476, Spavinaw. _LeFlore_: OU 16802, 1.5 mi.
E Zoe. _Osage_: UMMZ 89628, Big Hominy Creek. _Pottawatomie_: OU
25175, 5 mi. SW Shawnee. _Rogers_: OU 7317, Verdigris River, 5 mi. W
Claremore; UMMZ 81473-74, near Garnett, Tulsa County; UMMZ 81475, 4
mi. NE Inola. _Sequoyah_: OU 9008, 2 mi. NE Gore; TU 13885, Little
Vian Creek, 1 mi. E Vian. _Texas_: OU 5005, 5 mi. SE Guymon. _Tulsa_:
TU 17061, Bird Creek "near" Skiatook, Osage County. _Woods_: CHNM
11809, Waynoka; OU 9432, 2.5 mi. W Waynoka; OU 9579, 9581-82, 1 mi. S
Waynoka.

TEXAS: _Hansford_: TTC 719, 10 mi. S, 2 mi. W Gruver. _Hutchinson_:
TTC 1090, Carson Creek, Turkey Track Ranch.

WYOMING: _Goshen_: USNM 7648, Fort Laramie. _Weston_: UMMZ 78080,
Beaver Creek.

NO DATA: CNHM 21687-88, 22925. SM 142 (locality of Waco, McLennan
County, Texas, believed in error). USNM 7649, 11625, 19622-23, 36412
(Illinois River).

_Records in the literature._--ARKANSAS: _Benton_: (Dowling, 1957:37).
_Chicot_: Lake Chicot. _Clark_: Terre Noir Creek, 13 mi. W
Arkadelphia. _Garland_: Ouachita River, Mountain Pine (Conant and
Goin, 1948:7). _Hempstead_: _Jefferson_: (Dowling, _loc. cit._).
_Lawrence_: Black Rock (Dellinger and Black, 1938:46). _Madison_:
_Scott_: _St. Francis_: (Dowling, _loc. cit._). _Washington_: near
Greenland (Dellinger and Black, _loc. cit._).

COLORADO: _Boulder_: Boulder Creek, E Boulder; Boulder Creek, 6 mi. S
and 1 mi. E Longmont. _Larimer_: Cache la Poudre River. _Logan_: 8 mi.
NE Sterling. _Morgan_: Platte River "near" Fort Morgan. _Otero_:
Purgatoire River at Higbee. _Prowers_: Arkansas River at Lamar.
_Weld_: Poudre River "near" Greeley; Evans. _Yuma_: Bonny Dam,
Republican River (Maslin, 1959:24-25).

IOWA: _Dickinson_: Little Sioux River, Okoboji Twp. (Blanchard,
1923:24). _Story_: Skunk River, 5 mi. NNE Ames (Conant and Goin,
1948:9).

KANSAS: _Allen_: Petrolia (KKA). _Barber_: 7 mi. S Sun City. _Butler_:
3 mi. SE Augusta (Burt and Hoyle, 1934:198). _Chase_: 10 mi. SW Olpe;
7 mi. SW Saffordville (Breukelman and Smith, 1946:112). _Cherokee_:
tributary of Spring River, 1 mi. N Riverton (Hall and Smith,
1947:451). _Coffey_: (Smith, 1956:160, symbol on map). _Cowley_: 11
mi. SE Winfield (Stejneger, 1944:55). _Crawford_: Pittsburg (Hall and
Smith, _loc. cit._). _Doniphan_: "near" Geary (Linsdale, 1927:81).
_Elk_: (Smith, _loc. cit._). _Ellis_: Big Creek (Brennan, 1934:190);
Ellis (Conant and Goin, 1948:2). _Franklin_: Middle Creek, SE part of
county (Gloyd, 1928:135). _Greenwood_: (Stejneger, _op. cit._:54).
_Leavenworth_: Missouri River "near" Fort Leavenworth (Brumwell,
1951:208). _Lyon_: 5 mi. E Emporia (Breukelman and Smith, _loc.
cit._). _Marion_: (Smith, _loc. cit._). _Meade_: Meade County State
Park, _ca._ 13 mi. SW Meade (Tihen and Sprague, 1939:505). _Ness_:
5.5 mi. NW Ness (Breukelman and Smith, _loc. cit._). _Osage_: Marais
des Cygnes River; Long and Jordan Creeks (Clarke, 1958:21). _Reno_: 6
mi. E Turon. _Sedgwick_: 2 mi. NE Cheney (Burt, 1935:321). _Sheridan_:
State Lake 7 mi. NE Quinter, Gove County (Breukelman and Smith, _loc.
cit._). _Wabaunsee_: Dragoon Creek at Harveyville (Clarke, 1956:215).
_Wallace_: (Burt, 1933:208). _Wilson_: Fall River, 1/2 mi. S Neodesha
(Clarke, _loc. cit._).

MINNESOTA: _Anoka_: _Benton_: _Chisago_: (Breckenridge, 1944:184,
symbols on map). _Crow Wing_: (Breckenridge, _op. cit._:185).
_Dakota_: (Hedrick and Holmes, 1956:126). _Goodhue_: (Breckenridge,
_op. cit._:184, symbol on map). _Hennepin_: Minneapolis; Lake
Minnetonka (Breckenridge, _op. cit._:187); 5 mi. N. Minneapolis
(Breckenridge, 1955:5). _Houston_: Root River near Hokah. _Lesueur_:
Lake Washington (Hedrick and Holmes, _loc. cit._). _Meeker_: Swan Lake
(Breckenridge, 1957:232). _Pine_: (Breckenridge, 1944:185). _Ramsey_:
_Rice_: _Sherburne_: _Stearns_: (Breckenridge, _op. cit._:184, symbols
on map). _Washington_: just north of Stillwater (Hedrick and Holmes,
_loc. cit._). _Winona_: Winona (Breckenridge, _op. cit._:187). _Yellow
Medicine_: (Breckenridge, _op. cit._:185). _County unknown_ (Goodhue
or Wabasha): Lake Pepin (Breckenridge, _op. cit._:184).

MISSOURI: _Boone_: east of Ashland (Henning, 1938:92). _Jackson_:
Missouri River "near" Atherton (Anderson, 1942:219). _Jefferson_:
Mississippi River "near" mouth Glaize Creek at Sulphur Springs; Glaize
Creek at Barnhart (Boyer and Heinze, 1934:199). _St. Clair_: Osage
River "near" Osceola. _Vernon_: Marmaton River, 7 mi. N Moundville
(Conant and Goin, 1948:9).

MONTANA: Yellowstone River (Conant and Goin, 1948:9).

NEBRASKA: _Adams_: 1 mi. N Ayr (Hudson, 1942:101). _Dawson_: 2 mi. SE
Gothenburg (Gehlbach and Collette, 1959:142). _Franklin_: 2 mi. SW
Naponee. _Gage_: 1 mi. W Barnston. _Hitchcock_: 3 mi. E Stratton.
_Holt_: Elkhorn River "near" Atkinson. _Lancaster_: Lincoln (Hudson,
_loc. cit._). _Lincoln_: 1 mi. S Sutherland (Gehlbach and Collette,
_loc. cit._). _Red Willow_: 14 mi. NW McCook. _Richardson_: 2 mi. S
Rulo. _Wheeler_: 2 mi. W Ericson (Hudson, _loc. cit._).

OKLAHOMA: _LeFlore_: Wister (Conant and Goin, 1948:9); Shady Pointe
(KKA); Poteau River, 6.5 mi. W Heavener (Trowbridge, 1937:301).
_Tulsa_: Arkansas River "near" Tulsa (Force, 1930:38).

WYOMING: _Goshen_: Platte River (Conant and Goin, 1948:10).

=Trionyx spinifer asper= (Agassiz)

Gulf Coast Spiny Softshell

Plates 37 and 38

_Aspidonectes asper_ Agassiz, Contr. Nat. Hist. United States,
1(Pt. 2):405; 2(Pt. 3):pl. 6, fig. 3, 1857.

_Trionyx spinifer asper_ Schwartz, Charleston Mus. Leaflet,
No. 26:17, pls. 1-3, map 2, May, 1956.

_Platypeltis agassizii_ Baur, Amer. Nat., 22:1121, 1888.

_Type._--Lectotype, MCZ 1597; alcoholic female; locality designated as
Pearl River, Columbus, Marion County, Mississippi; received from Mr.
Winthrop Sargent of Natchez, Mississippi.

_Range._--Southeastern United States except peninsular Florida from
the Florida Parishes of Louisiana east to southern North Carolina;
Gulf Coast drainage including that of Lake Pontchartrain, Louisiana,
eastward to the Apalachicola River system, and Atlantic Coast drainage
including that of the Altamaha River in Georgia northward to the Pee
Dee River drainage in South Carolina (see map, Fig 19).

_Diagnosis._--Juvenal pattern of black ocelli and spots, and two or
more black, interrupted, lines paralleling rear margin of carapace;
pale postocular and postlabial stripes often united on side of head;
length of plastron short.

_Description._--Plastral length of smallest hatchling, 2.9 centimeters
(USNM 134244); of largest male, 13.2 centimeters (TU 17117); of
largest female, 27.0 centimeters (TU 13474).

Blackish marginal rings on carapace number two, three or four
posteriorly, but decrease in number anteriorly; segments of marginal
rings may extend to nuchal region; marginal rings increasingly
interrupted inwardly; pattern of hatchlings having well-defined
marginal rings that are not extensively interrupted (often males), or
having marginal rings broken into small segments or series of dots,
and pale outer margin of carapace marked by ill-defined, hazy, inner
border (often females); conspicuous marginal rings often lacking on
hatchling females; pale rim of carapace not four or five times wider
posteriorly than laterally; carapace having blackish dots, spots,
small ocelli or a combination thereof; marks on carapace of slightly
varying sizes, some occasionally barlike (usually males); some
hatchling females showing pale, irregular blotching on carapace, often
characterized by small lichenlike figures superimposed on blackish
dots.

Striping on snout variable; pale, dark-bordered stripes usually unite
in front of eyes and form right or acute angle; medial dark borders of
pale stripes on snout not joined anteriorly, broken into segments or
dots, reduced to single median line, united to form straight line
connecting anterior margins of orbits (usually with slight medial
indentation), or absent; pale postocular and postlabial stripes often
joined, relationship variable and on either side of head; side of head
with or without dark markings, sometimes a pale subocular blotch
bordered below by a dark line; pattern on dorsal portions of soft
parts of body contrasting, less so on limbs of hatchlings; pattern of
irregular dark marks, dark streaks usually coincident with digits;
longitudinal streaks often occur on neck; elongate tail of adult males
usually having well-defined, dorsolateral, pale bands with dark lower
border more diffuse than upper border.

Underparts whitish often with dusky markings on rear of carapace or in
region of bridge; blackish marks often on webbing and portions of
soles and palms, and chin and throat.

Small conical tubercles along anterior edge of carapace on adult
males; remnants of juvenal pattern usually present on carapace of
large females; conical or knoblike tubercles on anterior edge of
carapace of large females; accessory knoblike tubercles in nuchal
region (a paravertebral pair usually most prominent), and posteriorly
in middle of carapace on large females.

Ontogenetic variation in PL/HW, mean PL/HW of specimens having
plastral lengths 7.0 centimeters or less, 3.87, and exceeding 7.0
centimeters, 4.94; ontogenetic variation in CL/CW, mean CL/CW of
specimens having plastral lengths 8.5 centimeters or less, 1.11, and
exceeding 8.5 centimeters, 1.16; mean CL/PCW, 1.71; mean CL/PL, 1.45.

_Variation._--The sex of some hatchlings can be distinguished by the
pattern on the carapace (see Plate 37 for different patterns), but the
sex of many hatchlings cannot be distinguished on the basis of
pattern.

In the early stages of this study, I thought that the pattern on the
carapace differed in eastern and western populations, and that the
zone of intergradation was in Alabama. Adult males from the
Tombigbee-Alabama river drainage and westward were noted to have
blackish spots (some slightly ocellate) intermixed with few, if any,
smaller blackish dots, whereas the adult males from east of the
Tombigbee-Alabama river drainage had many small, black dots intermixed
with slightly larger, mostly ocellate marks (see Plate 38, left, top
and bottom, for contrast); also, hatchlings from western populations
were never observed to have four marginal rings. On the basis of
pattern, I would have thought that the individual having many ocelli,
that lacks correct locality data and that is photographed by Stejneger
(1944:Pl. 26), came from Georgia or South Carolina; but, the pattern
(_op. cit._:Pl. 27) of a specimen, probably an adult male, from South
Carolina, resembles the pattern on adult males from Louisiana. The
differences noted above are probably due to individual variation
rather than geographic variation.

Color notes taken from life of a freshly-killed adult male (TU 16071,
Louisiana) are: carapace olive, spots blackish, outer rim buff; top of
head olive, postocular and postlabial stripes yellow with blackish
borders, stripes on snout buff with blackish borders; dorsal ground
color of soft parts of body pale olive-green, larger marks blackish,
ground color laterally toward juncture of pattern and immaculate
undersurface, and toward insertions of neck and limbs becoming
yellowish; webbing on hind limbs having reddish tinge; dorsolateral
bands on tail yellow with blackish borders; undersurface whitish; chin
and throat olive-green with blackish marks; becoming buff then whitish
posteriorly.

[Illustration: FIG. 20. Basicranial length and ratio of greatest
diameter of internal choanae to least width of maxillary
bridge (IC/MB) on 30 skulls of _T. ferox_ (open circles),
26 of _T. spinifer_ (crosses), and 12 of the _agassizi_-form
(solid circles; half shaded circle represents holotype of
_agassizi_). Skulls of the _agassizi_-form tend to have
slightly smaller internal choanae than those of _spinifer_
or _ferox_.]

Occasional specimens have only one definite dark line paralleling the
rear margin of the carapace. Schwartz (1956:16) reported that
Charleston Museum No. 55.159.26 has only one solid line at the margin
of the carapace, and I received an adult male (KU 47120) reported to
have come from the Pearl River that is aberrant in not having more
than one dark marginal line. USNM 95191, a large stuffed female from
the Pearl River is mentioned by Stejneger (1944:59, Pl. 17) as having
marks that "assume the form of short lines parallel with the
submarginal ring"; I examined this specimen and noted that it had only
one dark marginal line. Stejneger (_op. cit._:64) mentioned another
from the Pearl River drainage, and Crenshaw and Hopkins (1955:20)
wrote that some individuals from Georgia have only one dark marginal
line. Presumably MCZ 1606 (now in the Albany Museum) recorded by
Stejneger (_op. cit._:52) as _Amyda s. spinifer_ from Columbus,
Georgia, is another specimen.

[Illustration: FIG. 21. Basicranial length and greatest width of
alveolar surface of maxilla on 52 skulls of _T. spinifer_ (open
circles) and 11 of the _agassizi_-form (solid circles; half shaded
circle represents holotype of _agassizi_). Most skulls of the
_agassizi_-form that exceed 43 mm. in basicranial length have a
more expanded, alveolar surface of the maxilla than skulls of
_spinifer_ of approximately the same size. All skulls exceeding
50 mm. are those of females.]

Some skulls of soft-shelled turtles from streams of the Atlantic Coast
drainage, including the skull of the holotype of _Platypeltis_ (=
_Trionyx_) _agassizi_ Baur (MCZ 37172, Pl. 54), show at least two
differences from other skulls of _asper_ and from those of other
subspecies of _T. spinifer_. Figure 20 shows that skulls of _agassizi_
tend to have slightly smaller internal choanae (ratio IC/MB) than
those of _T. spinifer_ and _T. ferox_; there is seemingly little
difference between skulls of _ferox_ and _spinifer_, and little, if
any, ontogenetic variation. Figure 21 shows that most skulls of the
_agassizi_-form that exceed 43.0 millimeters have a more expanded,
alveolar surface of the maxilla than skulls of _spinifer_ of
approximately the same size; most skulls exceeding a basicranial
length of 43.0 millimeters, and certainly all skulls exceeding 50.0
millimeters are those of females. Stejneger (1944:Pl. 30) also has
provided photographs of a skull of the _agassizi_-form. It is of
interest that of the 12 _agassizi_-form skulls (MCZ 37172; USNM 8708,
029034, 51981, 66859, 71681, 91282, 91310-11, 92521, 92583-84) that I
examined some resemble _ferox_ (Neill, 1951:9) in having the alveolar
surfaces of the jaws broadened, and the greatest width at the level of
the quadratojugal (Table 3, Plate 54); also, the localities of all 12
skulls are within the geographic range of _ferox_. Skulls of _ferox_,
however, have conspicuously broadened alveolar surfaces of the jaws
only when they exceed in length the largest skulls of _agassizi_. The
differences of skulls of the _agassizi_-form possibly reflect
isolation in the Atlantic Coast drainage, and an adaptation in feeding
habits. So far as I can ascertain, individuals occurring in rivers of
the Atlantic Coast drainage in Georgia and South Carolina (referable
to _agassizi_) do not differ consistently in external characters from
individuals of _T. s. asper_ that occur westward in the Apalachicola
drainage.

_Comparisons._--_Trionyx s. asper_ can be distinguished from all other
subspecies of _T. spinifer_ by usually having more than one black line
paralleling the rear margin of the carapace. This character and the
frequent fusion of the postlabial and postocular stripes on the side of
the head distinguish _asper_ from _spinifer_ and _hartwegi_. _T. s.
asper_ differs from _pallidus_, _guadalupensis_ and _emoryi_ in having
blackish spots and ocelli on the carapace, and lacking whitish dots or
tubercles. _T. s. asper_ resembles _spinifer_, _hartwegi_ and _pallidus_
but differs from _guadalupensis_ and _emoryi_ in having conical
tubercles along the anterior edge of the carapace in large females. For
additional differences see accounts of other subspecies.

Of the subspecies of _T. spinifer_, _asper_ has a proportionately wide
head that is closely approached in the subspecies _guadalupensis_ and
_emoryi_; _T. s. asper_ differs from _guadalupensis_ and _emoryi_ in
having a wider carapace, and resembles _hartwegi_ and _spinifer_, but
differs from the other subspecies in having the carapace widest at a
plane approximately one-half way back on the carapace. _T. s. asper_
differs from the other subspecies in having the shortest plastron.

_Remarks._--Stejneger (1944:72-74) has discussed the history of Baur's
_Platypeltis agassizi_. Briefly, Agassiz's description of _Platypeltis
ferox_ wherein he (1857:402) states that "The young ferox [Pl. 6, fig.
3] has two or three concentric black lines separating the pale margin
...," was applicable to _T. s. asper_. Agassiz mentioned also that the
young of his _Aspidonectes asper_ (_op. cit._:406) "as in Platypeltis
ferox, ... has ... two or three black lines separating the pale rim of
the posterior margin, ..."; however, _A. asper_ was distinguished
chiefly by the "... prominent warts of the bony plates (_loc. cit._)."
Because the description of the pattern of _ferox_ resembled that of
_asper_, the validity of _asper_ was not agreed upon by all workers.
Boulenger (1889:245, footnote 1) referred to _asper_ as a species that
required "... further investigation."

Baur (1888:1121) realized that Agassiz's description of _ferox_ was not
that of _Testudo ferox_ Schneider, and regarded the description of
Agassiz as applying to a new species, which he named _Platypeltis
agassizii_; Baur (_op. cit._:1122) also recognized _asper_, referring it
to the genus _Aspidonectes_. Baur designated a specimen from Georgia
(the only individual seen by him) as the type of _agassizi_ (Stejneger,
_op. cit._:73, footnote); this specimen is now MCZ 37172. Five years
later (1893:218), Baur discussed generic relationships of trionychids,
seemingly only on the basis of skulls (holotype of _agassizi_ not
mentioned), and referred _agassizi_ to the resurrected genus
_Pelodiscus_ Fitzinger, 1835, which was distinguished from the other two
American genera that Baur recognized (_Platypeltis_ and _Amyda_) by
having the "Posterior nares reduced in size by the inner and posterior
extension of the maxillaries." Baur also transferred _asper_ to the
genus _Platypeltis_, and restricted the type locality of that species to
"Lake Concordia, La." (_op. cit._:220); the type locality of _agassizi_
was restricted to "Western Georgia" (_loc. cit._).

The name-combination, _Pelodiscus agassizi_, was not generally accepted.
Hay (1892:144) and Siebenrock (1924:188) referred _agassizi_ to the
genus _Trionyx_. Hay regarded _agassizi_ as a full species (see
discussion by Stejneger, 1944:73), whereas Siebenrock considered it a
subspecies of _spiniferus_; both authors regarded _asper_ as a synonym
of _agassizi_. Neither _asper_ nor _agassizi_ was mentioned in the first
three editions of the Check List of North American Amphibians and
Reptiles (Stejneger and Barbour, 1917, 1923, 1933); the same authors in
the fourth (1939:171, 172) and fifth editions (1943:212, 213) listed
_agassizi_ as a full species, and _asper_ as a subspecies of
_spinifera_. Stejneger (1944) used the same arrangement as set forth in
the fourth and fifth editions of the Check List, and distinguished
_agassizi_ on the basis of cranial characters, namely, the small size of
the internal choanae, the greater width of the alveolar surface of the
lower jaw, and the position of the suture between the palatine and
basisphenoid relative to the posterior edge of the temporal fossa. Neill
(1951:9) regarded the peculiarities of the _agassizi_-type skull as
inconstant, but recognized _agassizi_ (and _asper_) as a subspecies of
_ferox_. Crenshaw and Hopkins (1955) showed that _asper_ did not
intergrade with _ferox_. Schwartz showed that _agassizi_ did not
intergrade with _ferox_, and regarded _agassizi_ as a synonym of _T. s.
asper_ (1956:17), but stated that _agassizi_ possessed "wider crushing
surfaces on the maxillae than does _T. s. asper_, even when skulls of
the same size and sex are compared" (_op. cit._:9).

The holotype of _Platypeltis agassizi_ (MCZ 37172) is a dried adult
female consisting of shell, skull and limb bones; the carapace is
approximately 300 millimeters long (Schwartz, _loc. cit._). I have
examined only the skull of MCZ 37172 (Plate 54), and it is the largest
of 12 _agassizi_-type skulls I have seen. The basicranial length is 72.5
millimeters, and the greatest width, which occurs at the level of the
quadratojugals, is 52.9 millimeters. The _agassizi_-type skulls have
been discussed under the subsection on variation.

The type locality of _T. s. asper_, Lake Concordia, Louisiana (lower
Mississippi River drainage) as restricted by Baur (1893:220), is in an
area of intergradation of three subspecies of _Trionyx spinifer_ where
most individuals are not typical of _asper_. The syntypes, the
designation of MCZ 1597 as a lectotype, and Pearl River, Columbus,
Marion County, Mississippi, as the type locality have been discussed
elsewhere (Webb, 1960).

The range of _T. s. asper_ overlaps that of _T. ferox_ in Georgia and
South Carolina. The two species remain distinct in the area of overlap
of their geographic ranges (Crenshaw and Hopkins, 1955:16; Schwartz,
_op. cit._:5). _Trionyx s. asper_ intergrades with _T. s. hartwegi_ and
_T. s. spinifer_ in the lower Mississippi Valley (Conant and Goin,
1948:11).

However, there are few specimens available that indicate intergradation
of _asper_ with the _spinifer-hartwegi_ complex in the lower Mississippi
River drainage; this may be due to the fact that _asper_ inhabits
waterways that do not drain into the Mississippi River. Perhaps
intergradation is more prevalent than the morphological basis that I
have relied upon indicates; in any event, there are few specimens that
have more than one dark marginal line (which is the only character that
is unique for _asper_) from the lower Mississippi drainage. A young male
(TU 11928.9) from Bayou Gauche between Paradis and Des Allemands, St.
Charles Parish, Louisiana, has a pattern on the carapace resembling that
of _asper_; several other small softshells (TU) are available from the
same locality but none shows more than one dark marginal line. Another
specimen (USNM 95192), a young female from a barrow pit of the Big Black
River (Mississippi River drainage), Madison County, Mississippi,
resembles _asper_ in having more than one marginal ring. Of three large
females from Moon Lake, an ox-bow of the Mississippi River in Coatopa
County, Mississippi (AMNH 5285-86, 5289), only 5289 shows evidence of
two marginal lines. USNM 73669 (Greenwood, LeFlore County, Mississippi)
also indicates intergradation in that the spots tend to be linear just
inside the dark marginal line, but the specimen more closely resembles
the _hartwegi-spinifer_ complex rather than _asper_.

There seems to be little adumbration of the dark marginal lines of
_asper_ in populations from the lower Mississippi River drainage.
Blackish spots and ocelli vary in size and there are many kinds of
pattern on the carapace. Soft-shelled turtles inhabiting the Mississippi
River and its tributaries in Louisiana and Mississippi certainly
represent an intergrading population of _spinifer_ and _hartwegi_, and,
to a lesser extent, of _asper_. Soft-shelled turtles inhabiting the
Pearl River drainage and rivers that drain into Lake Pontchartrain
immediately adjacent to the east are predominantly _asper_.

Specimens having localities from the Pearl River and Lake Pontchartrain
drainages are listed under the account of _asper_ and are referred to
that subspecies on the distribution map; specimens from the Mississippi
drainage in Mississippi are referred to _spinifer_.

One specimen (UMMZ 59198, Bradley County, Tennessee), from the Tennessee
River drainage where _T. s. spinifer_ occurs, deviates markedly from
_spinifer_ and suggests intergradation. UMMZ 59198, plastral length 4.8
centimeters, has ocelli in the center of the carapace only two
millimeters in diameter, a distinct but interrupted, second marginal
ring consisting of spots, and the pale postlabial and postocular stripes
in contact on both sides of the head.

_Specimens examined._--Total 110, as follows: ALABAMA: _Barbour_: UMMZ
113038, Chattahoochee River, Eufala. _Cherokee_: ANSP 24592, "near"
center of Terrapin Creek. _Conecuh_: UMMZ 70736, Murder Creek,
Castleberry. _Escambia_: TU 15823, Escambia River, 1 mi. N Sardine; UMMZ
70734, Escambia River at Flomaton. _Henry_: TU 15630, 3 mi. NW jct. Echo
Farm Rd. and Rt. 136 on Echo Farm Rd. _Lowndes_: UMMZ 67759, Pintlalla
Creek. _Mobile_: MCZ 1608 (2), 1608A, Mobile. _Sumpter_: USNM 83996, 3
mi. SE Coatopa. _Tuscaloosa_: TU 14673 (5), Black Warrior River, 17.5
mi. SSW Tuscaloosa; UA 52-1085, Cottondale. _Walker_: KU 50843, 50851,
TU 17137, Mulberry Fork, Black Warrior River, 9 mi. E Jasper.

FLORIDA: _Calhoun_: KU 50837-38, Chipola River, 4 mi. N Scott's Ferry;
TU 16689 (4), Chipola River "near" Blountstown. _Escambia_: TU 13474,
15869 (3), 16584, Escambia River, 1.2 mi. E Century. _Okaloosa_: TU
15661, Blackwater River, 4.3 mi. NW Baker on Route 4. _Santa Rosa_: AMNH
44621, Blackwater River, Milton. _Walton_: UMMZ 110421, Pond Creek, 4
mi. SW Florala, Covington County, Alabama.

GEORGIA: _Baker_: TU 15889 (3), USNM 134243-48, Flint River "near"
Newton; USNM 30822. _Baldwin_: USNM 8708, Milledgeville. _Bryan_: TU
15090, Canouche River, 2.3 mi. W Groveland. _Chatham_: USNM 51981,
92583-84, Savannah. _Chattooga_: UMMZ 113037, tributary of Chattooga
River, Lyerly. _Decatur_: KU 50839-42, Flint River, 1.5 mi. S
Bainbridge. _Fulton_: UMMZ 53037, Roswell. _Lincoln_: USNM 91282-83,
above Price Island, Savannah River. _Murray_: UMMZ 59196, 9 mi. N Spring
Place. _Pulaski_: TU 14882, Ocmulgee River, 4.3 mi. SE Hawkinsville.
_Richmond_: USNM 66859, Augusta. _Whitfield_: UMMZ 74209, Cohulla Creek,
Prater's Mill "near" Dalton. _County unknown_: MCZ 37172; UMMZ 109864,
Flint River at mouth of Dry Creek; USNM 029034.

LOUISIANA: _East Baton Rouge_: LSU 11, 1643-44, City Park Lake in Baton
Rouge; TU 17237, Amite River "near" Baton Rouge. _St. Tammany_: TU 6356,
headwater creek of Bayou Lacombe; TU 16071, USNM 66147, mouth of
Tchefuncta Creek in Lake Pontchartrain. _Tangipahoa_: TU 13623, 3.1 mi.
W Hammond; USNM 68054, Robert. _Washington_: KU 50840, 50846, TU 17117,
Pearl River at Varnado. _Parish unknown_ (East Baton Rouge or
Tangipahoa): UMMZ 95614, Manchac.

MISSISSIPPI: _Chickasaw_: USNM 115981, Chookatonkchie Creek. _Clarke_:
USNM 79350-51, 1 mi. W Melvin, Choctaw County, Alabama; USNM 100805,
Enterprise. _Forrest_: WEB 55-586, 1 mi. S Hattiesburg. _Hancock_: AMNH
46780; WEB 54-651, Hickory Creek "near" Kiln. _Lauderdale_: UMMZ 74681,
9 mi. W Meridian; UMMZ 90130, Lake Juanita, 15 mi. W Meridian.
_Lawrence_: KU 47120, TU 17307.1, Pearl River, 9 mi. S Monticello; USNM
7653-54, Pearl River at Monticello. _Lee_: CM 31904, Verona; USNM
115979, Cower's Area near Guntown. _Madison_: USNM 95191, 95193-94,
Pearl River. _Marion_: MCZ 1597, Pearl River at Columbus (designated
type locality). _Pearl River_: CM 21100, Pearl River, 20 mi. W
Poplarville; TU 14362, Hobolochito Creek, 1 mi. N Picayune. _Perry_: WEB
55-580, Beaver Dam Creek, 1 mi. N Richton. _Walthall_: KU 50844, Bogue
Chitto River, Dillon.

SOUTH CAROLINA: _Abbeville_: USNM 7650, Abbeville? (reported by Pickens,
1927:113; locality considered in error by Stejneger, 1944:50; USNM 7650
having only one dark marginal line paralleling rear margin of carapace
is possibly an aberrant specimen--see page 495 of present account).
_Greenwood_: USNM 71681, 73668, Greenwood. _McCormick_: USNM 91310-12,
Savannah River, 5 mi. W Plum Branch; USNM 92521, near Parksville.
_Richland_: AMNH 70724-25, Broad River, Columbia.

NO DATA: USNM 8359 (erroneously reported from Madison, Indiana by
Yarrow, 1882:29 and Hay, 1892:145; see discussion by Cahn, 1937:200, and
Stejneger, 1944:73-75); USNM 131859.

_Records in the literature._--ALABAMA: _Coffee_: Elba (KKA). _Marengo_:
Tombigbee River near Demopolis. _Mobile_: Fig Island (Löding, 1922:47).

FLORIDA: _Jackson_: Chattahoochee River, 8 mi. SE Butler. _Leon_:
Ochlocknee River, NW of Tallahassee (Goin, 1948:304).

GEORGIA: _Bartow_: Etowah River below Allatoona Dam, _ca._ 4 mi. ESE
Cartersville (Crenshaw and Hopkins, 1955:15). _Berrien_: (Knepton,
1956:324). _Emanuel_: Ogeeche River (Schwartz, 1956:19). _Fulton_: Nancy
Creek, Atlanta (Dunston, 1960:278). _Gwinnett_: _Irwin_: (Knepton, _loc.
cit._). _Jenkins_: Ogeeche River near Buckland Creek jct., 2.5 mi. S
Millen. _Liberty_: Camp Stewart, 4 mi. N Hinesville. _Morgan_: Lake
Rutledge (Schwartz, _loc. cit._). _Muscogee_: Columbus (Stejneger,
1944:52). _Wayne_: Altamaha River, 5 mi. N Mt. Pleasant (Schwartz, _loc.
cit._). _Wilcox_: Ocmulgee River, 3-4 mi. SSE Abbeville (Crenshaw and
Hopkins, _op cit._:16, footnote; Schwartz, _loc. cit._).

MISSISSIPPI: _George_: Whiskey Creek (Cook, 1946:185). _Harrison_: near
Biloxi. _Jackson_: Pascagoula Swamp, _ca._ 40 mi. E. Biloxi (Corrington,
1927:101). _Jones_: Eastabuchie. _Lee_: Cain Creek Bottom. _Lincoln_:
Old Brook Creek. _Lowndes_: Tombigbee River, Camp Henry Pratt and
Columbus; Lake Park, Columbus. _Pearl River_: 21 mi. SW Poplarville; 10
mi. W Poplarville; 4 mi. W Poplarville. _Wayne_: Trigg Area (Cook, _loc.
cit._).

NORTH CAROLINA: _Mecklenburg_: Catawba River near Charlotte (Schwartz,
1956:20).

SOUTH CAROLINA: _Aiken_: Savannah River, 10 mi. SW Jackson. _Allendale_:
Savannah River, Fennell Hill, 2 mi. S US 301. _Anderson_: Pendleton.
_Bamberg_: South Edisto River, Cannon's Bridge, 5 mi. from Bamberg.
_Berkeley_: 2.5 mi. W Pinopolis. _Charleston_: Charleston. _Clarendon_:
Upper Lake Marion at US 301; Lake Marion, 13 mi. SW Manning; 3.3 mi. S
Jordan; 6.3 mi. S Jordan; Wyboo Creek, 8.5 mi. from Manning. _Colleton_:
Edisto River (Schwartz, 1956:19-20). _Darlington_: Pee Dee River,
Society Hill (Stejneger, 1944:72). _Dorchester_: Edisto River, 17 mi.
from Summerville; Edisto River, 14 mi. W Summerville; Edisto River, 2.5
mi. S Hart's Bluff. _Fairfield_: 1 mi. N Peak, Newberry County.
_Georgetown_: North Santee River, 1 mi. above US 17. _McCormick_: Little
River near McCormick; Little River, 3 mi. NE Mt. Carmel. _Laurens_:
Enoree River, 3 mi. S Cashville, Spartanburg County; Enoree River, 9.4
mi. N Clinton. _Orangeburg_: Edisto River, Orangeburg. _Saluda_:
Batesburg; Lake Murray; Little Saluda River; 5 mi. from Saluda. _County
unknown_: Upper Lake Santee (Schwartz, _loc. cit._).

=Trionyx spinifer emoryi= (Agassiz)

Texas Spiny Softshell

Plates 43, 44

_Aspidonectes emoryi_ Agassiz (in part), Contr. Nat. Hist. United
States, Vol. 1, Pt. 2, p. 407; Vol. 2, Pt. 3, pl. 6, figs. 4-5,
1857.

_T[rionyx] s[pinifer] emoryi_ Schwartz, Charleston Mus. Leaflet,
No. 26, p. 11, 1956.

_Type._--Lectotype, USNM 7855; alcoholic (sex undetermined); obtained
from the Río Grande near Brownsville, Texas, in the course of the
Mexican Boundary Survey under the command of Colonel Wm. H. Emory.

_Range._--Southwestern United States and northern México; the Río
Grande drainage in Texas, New Mexico and northern México; the Río San
Fernando and Río Purificación drainages in northeastern México; the
Colorado River drainage in Arizona, New Mexico, and southern Nevada
(see map, Fig. 19).

_Diagnosis._--Juvenal pattern of white dots, not encircled with dusky
or blackish ocelli, confined to posterior third of carapace; pale rim
of carapace conspicuously widened, four to five times wider
posteriorly than laterally; a dark triangle in front of eyes, base
line connecting anterior margins of orbits; pale postocular stripe
interrupted leaving conspicuous pale, usually dark-bordered, blotch
just behind eye.

_Description._--Plastral length of smallest hatchling, 2.5 centimeters
(USNM 7632); of largest male, 13.0 centimeters (KU 2914, 3125, 3150);
of largest female, 22.0 centimeters (TNHC 8023, 8104).

Carapace pale brownish or tan, lacking whitish dots on anterior half;
whitish dots confined to posterior third of carapace, sometimes
lacking posteriorly, especially on juveniles; small, blackish dots
rarely occurring on surface of carapace, usually confined to margins
when present; pale rim of carapace four to five times wider
posteriorly than laterally.

Pattern on snout rarely variable, consisting of pale stripes extending
forward from eyes that have only their outer borders darkened and a
straight or slightly curved, dark line that connects anterior margins
of orbits; few, if any, dark markings in subocular and postlabial
region; pattern on side of head having few contrasting marks, often of
nearly uniform coloration; postocular stripe usually interrupted;
anterior segment of postocular stripe just behind eye usually
dark-bordered; posterior segment usually not dark-bordered or sharply
distinguished from background; pattern on dorsal parts of soft parts
of body contrasting, of relatively small dark marks; dark streaks
often coincident with digits.

Underparts whitish, occasionally having blackish dots or smudges on
posterior part of carapace, in region of bridge, or on lateral parts
of chin and throat; few dark marks often on webbing of limbs and on
palms and soles.

Small, flattened or wartlike, tubercles that occasionally have sharp
tips along anterior edge of carapace on adult males; tubercles
flattened, scarcely elevated, never conical along anterior edge of
carapace on large females; whitish, knoblike tubercles often present
posteriorly in middle of carapace and in nuchal region on large
females; mottled and blotched pattern sometimes contrasting on
carapace of large females; whitish dots of juvenal pattern often
visible through overlying blotched pattern of large females.

Ontogenetic variation in PL/HW, mean PL/HW of specimens having
plastral lengths 7.0 centimeters or less, 3.68, and exceeding 7.0
centimeters, 5.19; ontogenetic variation in CL/CW, mean CL/CW of
specimens having plastral lengths 8.5 centimeters or less, 1.17, and
exceeding 8.5 centimeters, 1.27; mean CL/PCW, 2.18; mean HW/SL, 1.43;
mean CL/PL, 1.37.

_Variation._--Ten topotypes (six males, three females, one juvenile)
from Brownsville, Texas (BCB 7465-73, 7564), have the following
characteristics: pale rim widened posteriorly as described above;
females (plastral lengths 9.8, 10.2 and 11.7 cm.) having blackish
marks in pale rim, which are absent in males of corresponding size;
interrupted postocular stripe with pale blotch behind eye; postocular
pale blotch having blackish borders or not; dark triangular mark on
snout in front of eyes; white dots present only on posterior third of
carapace; carapace of females grayish, blotched pattern not
contrasting; carapace of males paler, greenish-gray; undersurface
immaculate except 7468 and 7472 that have blackish flecks at bridge
and, on 7472, blackish marks that extend posteriorly onto ventral
surface of carapace; tubercles along anterior edge of carapace
flattened and rounded in adult males, more knoblike in females;
largest specimen, BCB 7472, female, plastron 11.7 centimeters long.

_T. s. emoryi_ varies more than any other subspecies of _Trionyx
spinifer_. A large series of males and females (KU) from the Salt
River (Colorado River drainage), near Phoenix, Arizona, is
characterized by many adult males having indistinct white dots on
posterior half of carapace; blotching on carapace of females of
contrasting lichenlike figures, but usually non-contrasting and pale
brownish or tan; pale rim of carapace distinct from ground color of
carapace in largest female (KU 2905, plastron 21.5 cm. in length), but
having dark or dusky markings: dark interorbital stripe often lacking.
AMNH 58370 (Nevada) and UMMZ 92006 (Arizona) also have the dark line
connecting the anterior margins of the orbits interrupted; seemingly
the dark interorbital line is most often interrupted in those
softshells inhabiting the Colorado River system of Nevada and Arizona.

Other variant individuals are: TU 14453.2, 14462 and 3696 having the
plastron extending slightly farther forward than the carapace, thus
resembling _T. ferox_; UMMZ 54021 and CNHM 39999, hatchlings, lacking
distinct whitish dots on posterior half of carapace; UI 43509 and KU
39991 having stained (brown or blackish) claws; and, CNHM 6810, an
adult male, lacking a spinose (sandpapery) carapace. I am unable to
discern geographic variation in these or other characters.

The ground color of the carapace on some individuals from the Pecos
River (TU, Terrell County, Texas) is grayish and in contrast with the
pale rim (Pl. 44). UI 43509 from the Río Florida, La Cruz, Chihuahua,
a female, has a dark brownish carapace with little evidence of a
blotched pattern except on the pale rim of the carapace. A female and
adult male from the Río Sabinas, Coahuila (MSU 905-06), also show
considerable darkening on the dorsal surfaces; the pale rim is evident
but not in sharp contrast to the coloration of the carapace. Notes
taken on the freshly-killed Sabinas individuals are: male--carapace
olive-gray; dorsal surface of soft parts of body olive-green to
grayish, a bright yellow suffusion on limbs and neck; female--carapace
and soft parts of body dark olive, laterally pale yellow; the plastron
extends slightly farther forward than the carapace in both sexes.

Notes on coloration (judged to be the most common or "normal" type)
of living _emoryi_ from the Río Mesquites, central Coahuila, are:
Adult male (KU 53753)--pale rim butterscotch yellow; marginal line
blackish; whitish dots on pale brown or tan carapace; soft parts of
body olive or olive-green, slightly darker on head and paler
(yellowish) on hind limbs; pale areas on side of head pale yellow,
having tint of orange on neck; ventral surface white, yellow laterally
on neck. Adult female (KU 53754)--carapace having contrasting blotched
and mottled pattern of pale browns and tans; soft parts of body olive
brown, darker brown blotching on head; dorsal surface of limbs
olive-green having pale areas lemon yellow and webbing butterscotch
yellow; side of neck and head, chin and throat pale lemon yellow;
ventral surface white having slight red tinge to groin and soft parts
posteriorly; underside of carapace near edge pale yellow.

Softshells from the Río Grande in the Big Bend region of Texas, and
the Río Conchos in Chihuahua differ from other specimens of _emoryi_.
Fifteen adult males, KU 51187-201 (no females in sample), were taken
from the mouth of the Río San Pedro at Meoquí, Chihuahua (see KU
51194, Pl. 44). They are noteworthy because of a conspicuous orange or
orange-yellow on the side of the head. Another relatively consistent
character is the blackish tip of snout (excepting 51199), although the
degree (palest on 51190) and extent of pigmentation posteriorly on the
snout is variable. Eleven males, KU 51175-85, from approximately 100
miles northeastward in the Río Conchos near Ojinaga, Chihuahua, also
have the bright orange on the side of the head; the tip of the snout
is not blackish, although in some it is slightly darkened. Three
females, KU 51174, 51186 (from Ojinaga) and 51173 (from 8 mi. S, 16
mi. W Ojinaga), lack the orange on the side of the head; KU 51186 has
a plastral length of 8.0 centimeters, whereas the other two females
have the same plastral length of 16.5 centimeters (larger than any
male). Nineteen adult males, KU 51965-72, 51980-90, from the Río
Grande near Lajitas also have the orangish coloration on the side of
the head, whereas twenty females, KU 51954-64, 51973-79, 51991-92
(three smaller than largest male) lack the coloration. The tip of the
snout is not blackish on any turtle in the series from Lajitas. The
smallest female, from Lajitas, having a plastral length of 6.9
centimeters, has a mottled carapace.

The orange of males is most conspicuous in the pale postocular and
postlabial areas; the stripes of the snout (distally) and the color of
the neck at its juncture with the immaculate ventral surface are
orange-yellow. The orange coloration is confined to males (all
examined were sexually mature) and is probably not of seasonal
occurrence (see comments under secondary sexual variation). I have not
noticed this coloration in other males of the subspecies _emoryi_;
however, long-preserved males might be expected to lack the orange
color; the specimens mentioned above were initially preserved in
alcohol. KU 51179 (plastral length 8.2 cm., from Ojinaga) is the
smallest sexually mature male of the species _spinifer_ that I have
seen. Another character of note is the generally greater development
of the plastral callosities (resembling _muticus_) than in other
subspecies of _spinifer_ or specimens of _emoryi_; three small adult
males (KU 51177, 51990, 51987, plastral length 9.3, 9.9 and 9.1 cm.,
respectively) have large hyoplastral and hypoplastral callosities that
appear to touch medially, and callosities on the epiplastron and both
preplastra.

On July 8, 1953, an adult male of _T. spinifer_ was removed from a
hoop-net set in the Río Purificación at Padilla, Tamaulipas, México. I
was particularly impressed by the lack of whitish dots on the dark
carapace; the following notes were taken from the freshly-killed
specimen: carapace a uniform dark olive, lacking white dots and having
a yellowish rim widest posteriorly; tubercles on anterior edge of
carapace only slightly raised, inconspicuous; top of head olive with
few dots and streaks; a well-defined yellowish postocular stripe not
conspicuously interrupted; sharp contrast between dark olive on side
of head and pale ventral coloration; yellowish-orange ventrolaterally
on head; an uninterrupted slightly-curved line connecting the anterior
margins of the orbits; carapace pear-shaped; underparts whitish,
lacking markings. This specimen has since been destroyed. The only
other specimen I have seen from this locality is a hatchling (UMMZ
69412, Pl. 43), which has a pale brownish or tan carapace that lacks
whitish dots; it resembles _emoryi_ in other characters. Although the
absence of whitish dots is not distinctive, its combination with the
uniform dark olive carapace in adult males and the fact that the Río
Purificación is an isolated drainage system, suggests that
soft-shelled turtles from that river system may warrant further
taxonomic study.

_Comparisons._--From all other subspecies of _spinifer_, _T. s.
emoryi_ can be distinguished by having a pale rim on the carapace that
is four to five times wider posteriorly than it is laterally. This
character, unique for _emoryi_, combined with patterns on the snout,
side of head and carapace that are subject to little variation, permit
ready identification of the subspecies _emoryi_. _T. s. emoryi_
resembles _pallidus_, and _guadalupensis_ and differs from _spinifer_,
_hartwegi_ and _asper_ in having whitish tubercles or dots on the
carapace. _T. s. emoryi_ resembles _guadalupensis_ but differs from
_pallidus_, _spinifer_, _hartwegi_ and _asper_ in lacking conical
tubercles along the anterior edge of the carapace on large females.
For additional differences see accounts of other subspecies.

Some populations of _T. s. emoryi_ resemble _T. muticus_ in the size
at which sexual maturity is attained and in the development of the
plastral callosities. _T. s. emoryi_ has a wide head that resembles
that of _T. ferox_, _T. ater_, _T. s. asper_ and _T. s.
guadalupensis_; _T. s. emoryi_ also resembles _T. ferox_ and _T. ater_
but differs from the other subspecies of _T. spinifer_ and _T.
muticus_ in having a narrower carapace. _T. s. emoryi_ resembles _T.
s. guadalupensis_, _T. s. pallidus_ and _T. ater_, and differs from
the other subspecies of _spinifer_ and _T. muticus_, in having the
carapace widest farther posteriorly than one-half way back on the
carapace. _T. s. emoryi_ resembles _T. ferox_ in having the shortest
length of snout of the subspecies of _spinifer_. The plastron is
shorter than in _T. ferox_, longer than in _T. s. asper_, and about
the same length as in _T. muticus_ and the other subspecies of _T.
spinifer_.

_Remarks._--Agassiz (1857, 1:407-08) did not designate a holotype in
the original description of _Aspidonectes emoryi_; specimens are
mentioned from the lower Río Grande of Texas, near Brownsville, and a
stream of the Río Brazos drainage in Williamson County, Texas. The
description is applicable to _T. s. emoryi_ as herein restricted,
except for the statement that the white tubercles of young specimens
are "encircled by faint black lines"; that statement is presumably
based on the juveniles from Williamson County. _T. s. emoryi_ does not
occur in Williamson County, Texas. Barbour and Loveridge (1929:225)
listed MCZ 1909-10 and 1627 as cotypes. Stejneger (1944:65) mentioned
MCZ 1909, 1913 and USNM 7855 as cotypes; the legend for Plate 20 (_op.
cit._) refers to a drawing that "corresponds fairly closely with the
type (MCZ 1910) collected at Brownsville, Texas, by Col. Emory."

The syntypic series consists of seven specimens--MCZ 1627 (two
specimens) from Williamson County, Texas; MCZ 1909 (three specimens)
and 1910 from Brownsville, Texas; and USNM 7855 from Brownsville,
Texas. The listing of number 1913 by Stejneger is considered a
_lapsus_ for 1910 as MCZ 1913 is catalogued as a _Graptemys
geographica_ (in letter dated November 17, 1959 from Dr. Ernest E.
Williams). Stejneger's reference to MCZ 1910 as the type is considered
unintentional and an inadequate designation of a lectotype.

In the "remarks" column of the USNM museum catalog, number 7855 is
referred to as "Ag. Type." USNM 7855 is here designated as lectotype
of _Trionyx spinifer emoryi_. The lectotype is a young specimen
(female?) that is not easily sexed by external characters; the
plastron measures (in centimeters) 6.3 in length, the carapace 8.2 in
length and 7.0 in width, and the head 1.4 in width. The carapace is
pale brown having inconspicuous whitish dots posteriorly and a pale
rim that is approximately 6.8 times wider posteriorly (4.1 mm.) than
it is laterally (0.6 mm.). The slightly curved dark line connecting
the anterior margins of the orbits is dimmer than the dark lines that
extend forward from the eyes. The pale postocular stripes having
blackish, dotted borders are interrupted; there are no other markings
on the side of the head. The ventral surface is immaculate except for
a few dark dots on the right side of the carapace; the ground color is
pale brown or tan, but the upper layer of skin can be scraped away
revealing an underlying pale lavender-cream ground color. The
tubercles along the anterior edge of the carapace resemble small
rounded warts.

MCZ 1910 is an adult male _T. s. emoryi_ having a plastron 10.7
centimeters in length. The carapace is pale brown having a relatively
smooth anterior edge, inconspicuous whitish tubercles posteriorly, and
a pale rim five times wider posteriorly than laterally; the pattern on
the head resembles that of _emoryi_.

Each of three hatchlings of _T. s. emoryi_, 3.4, 3.5 and 3.9
centimeters in plastral length, bears an MCZ catalogue number of 1909.
The carapaces are dark tan or gray having pale rims 3.7, 5.2 and 5.2
times wider posteriorly than laterally, and white dots absent or
obscure posteriorly; two specimens have small blackish dots
paralleling the pale rim posteriorly. The patterns on the heads are
referable to _emoryi_.

The two juvenal syntypes (5.2 and 6.1 cm. in plastral length) from
Williamson County, Texas, are both catalogued as MCZ 1627, but only
one of these bears a catalogue number. The two softshells are not
_emoryi_, and are more nearly like _T. s. guadalupensis_ than _T. s.
pallidus_. Actually, they are from an area of intergradation between
those subspecies (see comments concerning intergradation under the
accounts of the subspecies _pallidus_ and _guadalupensis_). White
spots occur on the carapaces anteriorly and posteriorly, the larger
(more posterior) of which are encircled with dusky ocelli. The
carapace of the small specimen (bearing no number) is brown having a
few, small black specks intermixed with the white spots. The carapace
of the large specimen is pale lavender and has a more obscure pattern
than the other specimen.

After Agassiz's description, _emoryi_ was accepted as a distinct
species. Neill (1951:15) suggested that _emoryi_ was subspecifically
related to _T. ferox_. Crenshaw and Hopkins (1955) and Schwartz
(1956), however, demonstrated that _ferox_ was a distinct species;
_emoryi_ has since been considered a subspecies of _T. spinifer_.

Two specimens having blackish dots on the carapace, indicate
relationship with _T. s. guadalupensis_. USNM 7638, a hatchling, has
large whitish dots surrounded by blackish dots confined to the
posterior half of the carapace, and the locality for this specimen is
merely Río Bravo (= Río Grande). CNHM 47366, a hatchling from Sierra
de las Palmas (Sierra de Santa Rosa, La Palma), Coahuila, has a few,
small, blackish dots, irregularly spaced, on the anterior half of the
carapace, but other dots more evenly distributed on the posterior half
where they are intermixed with whitish dots. The drawing of the dorsal
view of a hatchling _emoryi_ (Agassiz, 1857:Pl. 6, Fig. 4) shows a
sprinkling of blackish dots on the anterior half of the carapace. A
hatchling from Eagle Pass (USNM 116578) does not have a noticeably
widened pale rim posteriorly on the carapace, and is not
distinguishable from _pallidus_. See account of _T. s. guadalupensis_
for further comments on intergradation.

A soft-shelled turtle that was obtained in the Sacramento River by
three fishermen, near Sacramento, California, was named _Aspidonectes
californiana_ by Rivers (1889:233). A comparison (with _Aspidonectes
spinifer_ and _A. emoryi_) of certain features of the skull was
largely prepared by Baur and included in the description (_op.
cit._:234-35); seemingly, the most trenchant character of the skull of
_californiana_ was the enlarged alveolar surfaces of the jaws. This
feature prompted Baur (1893:220) to refer _californiana_ to the genus
_Pelodiscus_, which also included _agassizi_ (skulls also having jaws
with enlarged alveolar surfaces) and several Old World species. Van
Denburgh (1917) discussed the origin of the specimen that formed the
basis of River's description and concluded that it was brought over
from China. Siebenrock (1924:192) and Mertens and Wermuth (1955:389)
listed _Aspidonectes californiana_ as a synonym of _emoryi_. River's
description is not that of _emoryi_; the enlarged alveolar surfaces of
the jaws, and the dark carapace having tubercular ridges suggest a
resemblance to _T. ferox_. The papillae on the neck are not found in
any American species. Miller (1946:46, footnote 2) believed that "it
obviously was introduced, apparently from China," and cited Pope
(1935:61), who declared the specimen to represent _Trionyx sinensis_.

Schmidt (1924:64) first reported the occurrence of _T. s. emoryi_ west
of the continental divide in Arizona and suggested that it was highly
probable that the species had been introduced near Phoenix in recent
years. Cowles and Bogert (1936:42) mentioned a species of softshell
occurring in the Boulder Dam region and presumed the species to be
native to Asia and introduced by the Chinese. Linsdale and Gressitt
(1937:222) determined the status of the species in the Colorado River
drainage as _T. s. emoryi_. The discussions by Dill (1944:179-81) and
Miller (1946:46) indicate that _emoryi_ was introduced into the Gila
River (Colorado River drainage) in western New Mexico near the turn of
the century.

_T. s. emoryi_ and _T. ater_ are the only kinds of softshells
occurring in México. The colloquial name for soft-shelled turtles in
México is "tortuga blanca." This name is also used in reference to the
Central American river turtle, _Dermatemys mawei_, which occurs on the
east coast of México as far north as Veracruz.

_Specimens examined._--Total 275, as follows: ARIZONA: _Maricopa_:
CNHM 4768, KU 2214-19, 2803, 2824, 2837, 2903-07, 2909-16 (2914, 2
specimens), 2918-29, 3118-27, 3129, 3147-56, USNM 71627, Salt River,
Phoenix. _Pinal_: UI 37713, Gila River, 6 mi. E Winkleman; UMMZ
92006-07, Gila River, 1/2 mi. below Coolidge Dam; UMMZ 105824, San
Pedro River about 1 mi. above confluence with Gila River.

NEVADA: _Clark_: AMNH 58370, Boulder City boat landing, Lake Mead; TU
15802, Virgin River, Mesquite.

NEW MEXICO: _Eddy_: KU 15938, Carlsbad; KU 48217-18, Black River
Village. _Grant_: AMNH 79911, Gila River, 8 mi. NE Cliff.

TEXAS: _Brewster_: CNHM 39999, Tornillo Creek near jct. with Río
Grande; KU 51954-92, Lajitas; TCWC 4291, UMMZ 66471, USNM 45545,
103678, Boquillas; INHS 7975, UMMZ 114360, Hot Springs. _Cameron_: BCB
7564-73, CNHM 5339-40, 6810, MCZ 1909 (3), 1910, TU 11479-80,
11561-62, UMMZ 54021, 105209-13 (Brownsville Lake), USNM 7642, 7644,
7855, Brownsville; BCB 5121, 3 mi. S Harlington. _El Paso_: UMMZ
85085, El Paso; USNM 7641, 7701, El Paso del Norte. _Hudspeth_: USNM
20846, Fort Hancock on Río Grande. _Kinney_: CNHM 26090, Río Pinto W
of Bracketville; USNM 26426-36, Fort Clark. _Loving_: TTC 1143, Red
Bluff Lake just below dam on Pecos River. _Maverick_: TU 3696-97, UMMZ
116578, Eagle Pass. _Presidio_: TTC 628 (2), 632 (2), 3 mi. WNW
Lajitas, Brewster County. _Terrell_: TNHC 7997, 8022-23, Chandler
Ranch, 30 mi. S Sheffield, Pecos County; TNHC 8104, Dunlap Ranch, 25
mi. SE Sheffield, Pecos County; TU 14453 (7), 14462 (2), 15415, 15423,
15586, Pecos River near jct. with Independence Creek; USNM 104240,
Pecos River "near" Dryden. _Val Verde_: TTC 113, Pecos River. _Webb_:
TNHC 19788, 42 mi. NW Laredo; USNM 109078-79, Laredo. _Zapata_: UI
19332, "near" Zapata. _County unknown_: MCZ 1628, USNM 7635-36, 7854;
USNM 7637-38, Río Bravo (= Río Grande).

CHIHUAHUA: KU 51173, 8 mi. S, 16 mi. W Ojinaga; KU 51174-86, 1 mi. NW
Ojinaga; KU 51187-201, Río Conchos at mouth of Río San Pedro near
Meoquí; UI 43508-09, Río Florida, La Cruz.

COAHUILA: CNHM 26054, Sta. Helena Canyon of Río Grande; CNHM 28846,
"near" Músquis; CNHM 55657, Río Alamos, Rcho. de la Gacha; CNHM 47366,
Sierra de Santa Rosa, La Palma; CNHM 47367, 55661, Cuatro Ciénegas;
CNHM 55658-60, Rcho. de los Borregos near Juarez; KU 33523, La Presa
Don Martín; KU 39991, 39993, 8 mi. N, 2 mi. W Piedras Negras; KU
39992, 2 mi. W Jiménez; KU 46907, 16 km. S Cuatro Ciénegas; KU
46913-16, 10 km. S Cuatro Ciénegas; KU 53752-54, Río Mesquites, 8 mi.
W Nadadores; KU 53757, 8.5 mi. SW Cuatro Ciénegas; MSU 905-06, Río
Sabinas, 1 mi. E Sabinas.

NUEVO LEON: CNHM 1874, 2191, Rodriguez; UMMZ 69411, Río Conchos, 9 mi.
N Linares.

TAMAULIPAS: CM 3037, Nuevo Laredo. UMMZ 7614-20, 7622-25, 7628, 7630,
7632-33, Matamoros; UMMZ 69412, Río Purificación, N of Ciudad
Victoria.

NO DATA: MCZ 1629 (2), NHB 1032.

_Records in the literature._--ARIZONA: _Greenlee_: Gila River, Duncan
(Miller, 1946:46); "near" Sheldon (Dill, 1944:180). _Mohave_: Pierce's
Ferry just below lower end of Grand Canyon (Cowles and Bogert,
1936:42); 1.5 mi. upstream (Virgin River) from Mesquite, Clarke
County, Nevada (Hardy and Lamoreaux, 1945:168); Lake Havasu on
Colorado River (Dill, 1944:180). _Yuma_: Colorado River at Headgate
Rock Dam (Dill, _op. cit._:179).

CALIFORNIA: _Imperial_: California Lakes (Cowles and Bogert, 1936:42);
Palo Verde; Colorado River at Laguna Dam (Dill, 1944:180).

NEVADA: _Clark_: observed just north of Black Canyon (Cowles and
Bogert, _loc. cit._); Colorado River, 6 mi. N California line
(Linsdale, 1940:255).

NEW MEXICO: _Chaves_: Bitter Lakes Wildlife Refuge, 12 mi. NE Roswell
(Bundy, 1951:314). _Dona Ana_: Río Grande near Mesilla Dam (Little and
Keller, 1937:221).

TEXAS: _Brewster_: Río Grande at Castolon (Minton, 1959:38). _Val
Verde_: mouth of Devil's River (Brown, 1950:250).

BAJA CALIFORNIA: Colorado River delta, 7 mi. E Cerro Prieto; Imperial
Irrigation District, Alamo Canal, 15 mi. S Internat'l Boundary and
Salfatana Canal, 1 mi. N Black Butte (Linsdale and Gressitt,
1937:222).

COAHUILA: San Juan (Schmidt and Owens, 1944:103).

Hitherto, soft-shelled turtles of the species _Trionyx spinifer_ from
the southern and southwestern United States having a pattern of white
dots on the carapace have been relegated to the subspecies _emoryi_,
but my examination of soft-shelled turtles from Texas has indicated
that _T. s. emoryi_ as previously conceived, is a composite of three
subspecies. It is necessary, therefore, to recognize two new
subspecies.

=Trionyx spinifer guadalupensis= new subspecies

Guadalupe Spiny Softshell

Plates 41 and 42

_Holotype._--UMMZ 89926, alcoholic adult male; obtained 15 miles
northeast Tilden, McMullen County, Texas (Pl. 41, bottom, left).

_Paratypes._--Forty-two specimens: ANSP 16717 (hatchling), no data;
USNM 78515-16 (hatchlings), Colleto Creek, Victoria County, Texas; TU
10143-45, 10148, 10150-59, 10161-65 (adult males), TU 10176, 10833
(immature males), TU 10147, 10149, 10155 (immature females), TU 10160
(adult female), Guadalupe River, 9 miles southeast Kerrville, Kerr
County, Texas; UMMZ 89915-21, 89924-27 (adult males), UMMZ 89922-23
(immature females), same locality as holotype; UMMZ 92752 (immature
female), San Antonio River, 3 miles west-northwest Goliad, Victoria
County, Texas.

_Description of holotype._--Carapace nearly circular, widest at level
of posterior border of hypoplastra; margin entire; dorsal surface
"sandpapery" to touch; pale rim separated from ground color of
carapace by well-defined, blackish line that is wavy and narrowly
interrupted posteriorly and anteriorly; pale rim approximately 1.8
times wider posteriorly (5.4 mm.) than laterally (3.0 mm.); pale rim
increasingly narrower anteriorly, absent in nuchal region; tubercles
in nuchal region low, scarcely elevated, lacking sharp tips; ground
color of carapace olive having pattern of whitish spots and small
tubercles; most whitish tubercles inconspicuous pinpoints; other small
tubercles in center of whitish spots, mostly approximately 2
millimeters in diameter; largest white spot 3.4 millimeters in
diameter; most white spots surrounded by blackish ocelli or parts
thereof; whitish spots distributed over entire surface of carapace;
certain features of bony carapace evident through overlying skin;
carapace highest in region of second and third neurals, forming
obtuse, gently sloping, vertebral, keel; undersurface of carapace
butterscotch yellow, lacking markings; maximum length, 16.5
centimeters; greatest width, 13.5 centimeters.

Plastral surface butterscotch yellow, lacking markings, extending
slightly farther forward than carapace; anterior and posterior lobes
rounded; anterior lobe slightly truncate; certain features of bony
elements of plastron visible through overlying skin; maximum length of
plastron, 12.0 centimeters.

Head, extended to posterior level of eyes, terminating in flexible
snout; septal ridges projecting into each rounded nostril; jaws
closed, each covered by fleshy lips except anteriorly where horny
portions exposed; dark triangular mark in front of eyes, base line
connecting anterior margins of orbits forming series of dots; pale
stripes extending forward from eyes having faint inner, blackish
borders; eyelids partly open having blackish dots; pale subocular
blotch on right side of head having border of black dots.

Forefeet and hind feet well-webbed having five digits each; each limb
having nails on first three digits; each forelimb with four
antebrachial scales, three of these having free edge; each hind limb
with two horny scales, one smooth on posterodorsal surface and other
with free edge on posteroventral surface; pattern toward insertion of
forelimbs indistinct.

Tail terminating in flexible point; penis exposed; cloacal opening
extending beyond posterior edge of carapace; tail olive above bordered
by blackish marks; few black dots laterally on left side.

Undersurface of soft parts of body buff, lacking markings; few dark
marks posteriorly on webbing of limbs, encroaching on soles and palms.

_Range._--Southcentral Texas in the drainage systems of the Nueces and
Guadalupe-San Antonio rivers; the Colorado River drainage in Texas is
inhabited by a population that more closely resembles _guadalupensis_
than _pallidus_. See comments under subsection entitled "Remarks" and
Fig. 19.

_Diagnosis._--Juvenal pattern of white dots that are conspicuous on
anterior half of carapace, and usually as large as those on posterior
half; white dots, sometimes 3 millimeters in diameter, encircled with
blackish ocelli in adult males.

_Description._--Plastral length of smallest hatchling, 3.3 centimeters
(ANSP 16717); of largest male, 13.5 centimeters (TU 10162); of largest
female, 22.0 centimeters (TU 10160).

Hatchlings having white dots on anterior half of carapace; white dots
anteriorly nearly as large as those posteriorly, encircled with
blackish ocelli, and conspicuous on dark background (ANSP 16717, Pl.
41; USNM 78515-16; Stebbins, 1954:181, Pl. 26B), or smaller than those
posteriorly, not encircled with dusky ocelli, and inconspicuous on
pale background (TNHC 1446); pale rim of carapace less than four times
as wide posteriorly as laterally.

Adult males resembling holotype; size of white tubercles on carapace
variable; most, if not all, tubercles surrounded by narrow blackish
ocelli, or parts thereof; largest white tubercles or dots in most
specimens exceeding one millimeter and in some specimens three
millimeters in diameter (TU 10163); white dots often slightly elongate
(UMMZ 89917, 89920, 89926; TU 10152, 10145); juvenal pattern of white
dots seemingly more contrasting in _guadalupensis_, owing to dark
ground color of carapace, than in _pallidus_ or _emoryi_ that have
pale brown or tan carapaces; small tubercles along anterior edge of
carapace rounded, obtuse, wartlike, never conical; sharp tips often
lacking (TU 10153).

Large females often having whitish spots on anterior half of carapace
(TU 10160, Pl. 42, upper, right; 10142); carapace dark having
ill-defined mottled and blotched pattern; tubercles along anterior
edge of carapace low, rounded, rarely equilateral, never conical;
small blackish dots rarely on surface of carapace (UMMZ 89923).

Pattern on side of head and snout of little diagnostic value;
postocular stripe usually interrupted, but configuration variable,
consisting of pale anterior, dark-bordered segment (just behind eye);
posterior segment of postocular stripe usually less well-defined and
generally blending with adjacent ground color; pale postocular stripe
sometimes uninterrupted and dark-bordered throughout its length (TU
10157, 10159, 10176); pattern on dorsal surface of snout variable;
pattern usually consisting of uninterrupted dark line (slightly curved
anteriorly) connecting anterior margins of orbits (TU 10161, 10164,
10159, 10143), or dark line interrupted (TU 10153, 10154, 10176),
absent (TU 10163), or present in addition to dark inner borders of
pale stripes that extend anteriorly from eyes (TU 10149, 10162);
small, often fine, dark markings, on dorsal surface of limbs,
especially forelimbs; ventral surface of plastron and soft parts of
body usually whitish, lacking markings; small blackish spots
occasionally in region of bridge (TU 10149); dark marks occurring on
webbing of limbs and often encroaching on soles and palms.

Ontogenetic variation in PL/HW, mean PL/HW of specimens having
plastral lengths 7.0 centimeters or less, 3.83, and exceeding 7.0
centimeters, 5.18; ontogenetic variation in CL/CW, mean CL/CW of
specimens having plastron lengths 8.5 centimeters or less, 1.14, and
exceeding 8.5 centimeters, 1.22; mean CL/PCW, 2.11; mean HW/SL, 1.38
(including subspecies _pallidus_); mean CL/PL, 1.37.

_Variation._--Two hatchlings (ANSP 13447, Bexar County; TNHC 1446,
McMullen County) more closely resemble _pallidus_ than
_guadalupensis_.

Some individuals from the Colorado River drainage have features
suggesting those that are characteristic of _pallidus_. Large females
have obtuse, knoblike somewhat triangular-shaped tubercles along the
anterior edge of the carapace, which are never conelike (TU 14439-40,
10187, 16036.1; BCB 6010). The tubercles along the anterior edge of
the carapace are more elevated than in turtles from drainage systems
west of the Colorado. Whitish spots are usually absent anteriorly on
the carapace, but may be evident through the mottled pattern of large
females (BCB 6010, plastral length, 19.7 cm.). The pale postocular
stripe is usually interrupted, whereas the dark line connecting the
anterior margins of the orbits is usually not interrupted; the two
characters last mentioned show alliance with _guadalupensis_.

The carapace of hatchlings from the Colorado River is pale having
whitish dots, smaller anteriorly than posteriorly, which may be
encircled with dusky ocelli (TNHC 20257) or not (ANSP 11889, BCB 5055,
SM 3282). Many hatchlings are not distinguishable from _pallidus_
(TCWC 7262, TNHC 4975, SM 4924, 6106). I have not seen hatchlings from
the Colorado River that resemble ANSP 16717.

The pattern on the carapace of adult males from the Colorado River
drainage resembles that of _guadalupensis_ (Pl. 41, bottom, right) but
the whitish dots are usually smaller and may not be encircled with
blackish ocelli (BCB 4066, TU 14485). An adult male (TU 14476) from
the South Fork of the Llano River has whitish dots three millimeters
in diameter and encircled with blackish ocelli (_guadalupensis_),
whereas another adult male (USNM 83690) from a tributary of the
Colorado, the South Concho River, resembles _pallidus_.

Eight specimens from the San Saba River (TU 14419 [6 specimens],
14439-40), that range in plastral length from 6.8 to 17.0 centimeters
are impressive because of the dark brownish coloration on the
carapace. The smallest individual, which is also the only male in the
series, is paler. The mottled and blotched pattern on the females is
therefore not contrasting; the largest females have elevated whitish
prominences in the center of the carapace posteriorly. An immature
male (UMMZ 70348) from the South Concho River also has a dark brown
carapace, and lacks white dots. The dark coloration of the carapace of
these specimens recalls the TU series of _T. s. emoryi_ from the Pecos
River, Terrell County, Texas.

Color notes taken from a freshly-killed adult female from the Llano
River, two miles west Llano (TU 16036.1, Pl. 42), are: pattern on
carapace of dark olive or blackish marks that form an irregular
reticulum or marbling on a paler background that varies from brownish
to buff and has an orange or reddish tinge in some areas; small
whitish spots posteriorly; pale rim yellowish, evident only at sides
of carapace; dorsal surface of soft parts of body olive-green,
becoming paler with yellowish tinge toward insertions of limbs and
neck; no contrasting pattern on limbs or neck and head; yellowish on
sides of body; ventral surface whitish lacking dark marks, yellowish
at region of bridge, axillary region and on neck; chin olive-yellow.

_Comparisons._--_T. s. guadalupensis_ can be distinguished from all
other subspecies of _T. spinifer_ in having: (1) large white dots,
sometimes three millimeters in diameter, on a dark background usually
surrounded with blackish ocelli and conspicuous on the anterior half
of the carapace (some as large as those on posterior half) in adult
males, and (2) whitish dots on the anterior half of the carapace, in
hatchlings, that are often encircled with dark ocelli. _T. s.
guadalupensis_ resembles _pallidus_ and _emoryi_ in having white
tubercles or dots on the carapace and therein differs from _spinifer_,
_hartwegi_ and _asper_. _T. s. guadalupensis_ resembles _pallidus_ but
differs from _emoryi_ in having a pale rim that is less than four
times wider posteriorly than laterally. _T. s. guadalupensis_
resembles _emoryi_ but differs from _pallidus_, _spinifer_, _hartwegi_
and _asper_ in having along the anterior edge of the carapace
tubercles that are flattened or wartlike prominences often lacking
sharp tips in adult males; these tubercles are never conical in large
females.

_T. s. guadalupensis_ has a wide head, a feature shared with the
subspecies _asper_ and _emoryi_, but differs from _emoryi_ in having a
wider carapace. _T. s. guadalupensis_ resembles _emoryi_ and
_pallidus_ but differs from the other subspecies in having the
carapace widest farther posterior than one-half the length of the
carapace. The length of snout in _pallidus_ and _guadalupensis_ is
shorter than in _spinifer_ and _hartwegi_ but is longer than in
_emoryi_. _T. s. guadalupensis_ differs from _asper_ but resembles the
other subspecies in having a relatively long plastron.

_Remarks._--Some individuals of _guadalupensis_ have characteristics
that are applicable to _emoryi_. TNHC 12352 (Llano River) a hatchling,
has conspicuous white dots confined to the posterior third of the
carapace; the pale rim, however, is not widened posteriorly. TU 10156
(Guadalupe River) has a conspicuously widened pale rim on the carapace
that is approximately 3.4 times wider posteriorly (8.5 mm.) than
laterally (2.5 mm.).

_T. s. guadalupensis_ more closely resembles _pallidus_ than _emoryi_.
Turtles living in rivers that drain into the Gulf of Mexico east of
the Guadalupe-San Antonio river system successively show increasing
resemblance to _pallidus_ from west to east.

The expression of intergradation between _guadalupensis_ and
_pallidus_ is of a clinal nature that involves parallel changes in the
pattern on the snout, side of head, limbs (to a lesser degree),
tuberculation along the anterior edge of the carapace, size of whitish
tubercles or dots, and the distinctness of the blackish ocelli that
surround the whitish dots on the carapace. These characters form a
well-marked gradation or cline that extends over a considerable area.
There is, however, no continuous environmental gradient because the
populations are relatively isolated by occupying adjacent drainage
systems. The sharpest break in the gradation of characters mentioned
above occurs between the Colorado River and Brazos River drainages.
The population of softshells in the Colorado River drainage is
actually an intergradient one, but more closely resembles
_guadalupensis_, whereas the population in the Brazos River drainage
more closely resembles _pallidus_. For convenience the turtles
inhabiting the Colorado River drainage are referred to _guadalupensis_
and those in the Brazos River drainage to _pallidus_. Some individuals
from farther west than the Colorado River drainage will resemble
_pallidus_, and a few individuals from father east than the Brazos
River drainage will resemble _guadalupensis_.

The gradation of some of the characters mentioned above terminates in
the subspecies _emoryi_. It, however, has characters not found in
_pallidus_ or _guadalupensis_, and is more distinct from either of
those subspecies than either is from each other; the difference in
characters as well as the break in the gradient of characters between
_guadalupensis_ in the Nueces River drainage and _emoryi_ in the Río
Grande drainage is greater than that between _guadalupensis_ in the
Colorado and _pallidus_ in the Brazos River drainages.

I have refrained from designating individuals between these three
subspecies (_emoryi_, _guadalupensis_ and _pallidus_) as "intergrades"
on the distribution maps, and only mention (in text) those individuals
whose characters show a decided tendency toward the adjacent
subspecies. For further comments on intergradation see the account of
_T. s. pallidus_.

_Specimens examined._--Total 97, as follows: TEXAS: _Bandera_: KU
50834, Hondo Creek, 4 mi. W Bandera; TNHC 797-98, 7 mi. SW Medina.
_Bexar_: ANSP 13447, Helotes; MCZ 4587; USNM 10789, 71009, San
Antonio. _Borden_: BCB 4066, 7 mi. N Vincent. _Brown_: TNHC 7262, 1
mi. E Brownwood. _Comal_: USNM 7700, New Braunfels. _Dawson_: TNHC
21594-95, 10 mi. E Lamesa. _Frio_: USNM 7747, Río Seco. _Gillespie_:
TU 10185, 10187, 10205, Beaver Creek, "near" Doss. _Hays_: AMNH
29950-52, San Marcos. _Kerr_: SM 2553, headwaters Turtle Creek; TU
10142-45, 10147-65, 10176, 10833, Guadalupe River, 9 mi. SE Kerrville.
_Kimble_: BCB 5052-55, 6010, 3 mi. SE Telegraph; TU 14476, South Fork
Llano River, 1.5 mi. SE Telegraph; TU 14485, Llano River, 10 mi. W
Junction. _Lavaca_: SM 2554-55, 2559, 3 mi. NNE Hope. _Llano_: TNHC
12352, TU 16036 (2), Llano River, 2 mi. W Llano. _McMullen_: TNHC
1446, 10 mi. W Simmons, Live Oak County; UMMZ 89915-27, 15 mi. NE
Tilden. _Matagorda_: ANSP 11889, Matagorda. _San Saba_: SM 6106; TU
14419 (6), 14439-40, San Saba River, 11 mi. NNW San Saba. _Tom Green_:
SM 3282, UMMZ 70348, USNM 83690, South Concho River at Christoval.
_Travis_: SM 659-60, 8.5 mi. from mouth of Onion Creek in Colorado
River near Austin; SM 4924, Onion Creek; TNHC 4975, Upper Bull Creek;
TNHC 20257, Marshall Ford Dam. _Victoria_: CM 3118, Black Bayou; UMMZ
92752, San Antonio River, 3 mi. WSW Goliad; USNM 78515-17, Colleto
Creek, Guadalupe River. _County unknown_: ANSP 16717; TNHC 1404.

_Records in the literature._--TEXAS: _Bandera_: 24 mi. WNW Medina
(Brown, 1950:250). _Burnet_: Colorado River (Strecker, 1909:8).
_Gillespie_: 20 mi. N Harper (Brown, _loc. cit._). _Kendall_: Cibolo
Creek at Boerne (Strecker, 1926:8). _Kerr_: Guadalupe River, 3 mi.
above Kerrville (TCWC 474, listed in card file). _Mason_: 12 mi. NE
Mason (TCWC 3303, listed in card file). _Matagorda_: Bay City (Brown,
_loc. cit._). _Real_: (Stejneger, 1944:66). _Wilson_: Cibolo River, 30
or 40 mi. N Sutherland Springs (Strecker, 1935:23).

=Trionyx spinifer pallidus= new subspecies

Pallid Spiny Softshell

Plates 39 and 40

_Holotype._--TU 484, alcoholic adult male; obtained from Lake Caddo,
Caddo Parish, Louisiana on June 27, 1947, by Fred R. Cagle and party
(Pl. 39, lower, left).

_Paratypes._--Forty-two specimens: TU 481, 490, 678 (hatchlings), TU
381, 472, 488 (immature males), TU 475, 478, 486, 1232, 1291, 10170
(adult males), TU 399, 487 (immature females), TU 469 (adult female),
Caddo Lake, Caddo Parish, Louisiana; TU 15818 (immature male), TU
15819 (adult male), Cross Lake, Caddo Parish, Louisiana; TU 1253,
13211 (adult males), TU 13266 (immature female), Sabine River, 8 miles
southwest Merryville, Beauregard Parish, Louisiana; TU 13281-82 (adult
males), TU 13280, 13265 (immature females), TU 13303-04, 13306 (adult
females), Sabine River, 8 miles southwest Negreet, Sabine Parish,
Louisiana; SM 2375 (adult male), Wallace Bayou, De Soto Parish,
Louisiana; TU 1122 (adult male), Lacassine Refuge, Louisiana; UMMZ
92754 (adult male), 5 miles west Iowa, Calcasieu Parish, Louisiana; KU
40174-76, OU 27297 (adult males), OU 27290 (immature female), Lake
Texoma, 2 mi. E Willis, Marshall County, Oklahoma; KU 50832
(hatchling), mouth of Caney Creek, 4 miles southwest Kingston,
Marshall County, Oklahoma; CNHM 15474 (immature female), Kiowa County,
Oklahoma; KU 2966-67 (immature females), KU 2934, 2947 (adult males),
KU 2973 (adult female) Lewisville, Lafayette County, Arkansas.

_Description of holotype._--Carapace circular, widest at level of
posterior edge of hyoplastra; margin entire; dorsal surface
"sandpapery" to touch; pale rim separated from ground color of
carapace by well-defined, slightly ragged, blackish line; pale rim
approximately 2.1 times wider posteriorly (4.7 mm.) than it is
laterally (2.2 mm.); pale rim increasingly narrower anteriorly, absent
in nuchal region; tubercles along anterior edge of carapace triangular
with sharp tips becoming flattened and inconspicuous at level of
insertions of arms; ground color of carapace brownish having pattern
of small whitish tubercles; most whitish tubercles inconspicuous, of
pinpoint size, giving surface of carapace "sandpapery" effect; largest
white tubercles posteriorly, approximately 1.2 millimeters in
diameter; whitish tubercles smaller anteriorly, largest approximately
0.6 millimeters in diameter; whitish tubercles tend to form two
parallel lines coincident with longitudinal sutures of neurals
posteriorly in center of carapace; certain features of bony carapace
evident through overlying skin; carapace highest in region of third
and fourth neurals, forming obtuse, gently sloping, vertebral keel;
undersurface of rear margin of carapace whitish having pinkish tinge
and no markings; maximum length, 16.8 centimeters; greatest width,
14.3 centimeters.

Plastral surface extending slightly farther forward than carapace,
whitish having pinkish tinge and no dark markings; anterior and
posterior lobes rounded, posterior lobe more acutely; certain features
of bony elements of plastron visible through overlying skin; maximum
length, 12.2 centimeters.

Head extended, terminating in flexible snout; septal ridges projecting
into each rounded nostril; tip of snout darkened; jaws open, each
covered by fleshy lips except anteriorly where horny portions exposed;
dark triangular mark in front of eyes, base line uninterrupted,
slightly curved anteriorly, connecting anterior margins of orbits;
eyelids having blackish dots, especially upper, closing eyes; small
blackish dots on dorsal surface of head; pale postocular stripe
dark-bordered, interrupted; pale portion of stripe traversed by black
line; pale subocular blotch margined by broken blackish border; side
of head having contrasting blackish marks on pale background;
postlabial stripe having lower blackish border on right side of head;
chin with ill-defined marks, not contrasting on grayish background;
well-defined, ragged black line on side of neck separating dorsal
coloration from immaculate ventral coloration; small dark dots on
dorsal surface of neck; dorsal surface of head and neck olive or
brownish, becoming paler laterally and toward insertion of neck;
maximum width of head, 2.1 centimeters.

Forefeet and hind feet well-webbed each having five digits; each limb
having nails on first three digits; each forelimb with four
antebrachial scales, three of which have free edge; each hind limb
with two horny scales, one smooth on posterodorsal surface and other
with free edge on posteroventral surface; contrasting pattern of
blackish marks, mostly roundish, on pale background of grayish-white.

Tail terminating in flexible point; penis partly exposed; cloacal
opening extending beyond posterior edge of carapace; tail having
dorsal grayish band flanked by interrupted blackish lines; dark marks
encroaching ventrally at tip of tail.

Undersurface of soft parts of body whitish, with pinkish tinge; dark
marks lacking on soles, present on webbing and palms; dark marks
arranged in linear fashion coincident with digits.

_Range._--Southern Oklahoma, eastern Texas, extreme southwestern
Arkansas, and the western half of Louisiana; Red River drainage and
rivers that drain into the Gulf of Mexico east of the Brazos River
drainage in Texas and west of the Atchafalaya River drainage in
Louisiana. The Brazos River drainage is inhabited by a population that
more closely resembles _pallidus_ than _guadalupensis_ (see comments
under subsection entitled "Remarks"; see map, Fig. 19).

_Diagnosis._--Juvenal pattern of white dots that are usually absent or
inconspicuous, but sometimes distinct and small, on anterior third of
carapace, and not surrounded with dark ocelli; white dots often absent
on posterior half of carapace of hatchlings; white spots, rarely as
large as two millimeters in diameter, not encircled with black ocelli
on adult males; pale rim of carapace less than four times wider
posteriorly than laterally.

_Description._--Plastral length of smallest hatchling, 3.3 centimeters
(KU 50832); of largest male, 16.0 centimeters (SM 2375); of largest
female, 30.5 centimeters (TU 13213).

Surface of carapace in hatchlings uniform pale brown or tan; small
white tubercles absent or inconspicuous on anterior half of carapace,
but evident on posterior half of carapace, sometimes well-defined (TU
481), but usually inconspicuous (TU 678, 490); pale rim of carapace
less than four times wider posteriorly than laterally.

Adult males resembling description of holotype; small whitish
tubercles or dots rarely two millimeters in diameter on posterior half
of carapace, smaller and usually inconspicuous on anterior half of
carapace (TU 13281, 486); well-defined whitish tubercles occasionally
on anterior half of carapace (KU 40174); white tubercles not
surrounded with black ocelli; pattern of white dots seemingly less
contrasting in _pallidus_ than in _guadalupensis_, owing to pale brown
or tan carapace; small tubercles along anterior edge of carapace
equilateral or conical having sharp tips.

Large females usually having pale brown carapaces with slightly
contrasting, brownish, mottled and blotched, patterns; white
prominences often evident posteriorly and anteriorly in middle of
carapace and in nuchal region; tubercles along anterior edge of
carapace equilateral or conical in shape.

Pattern on side of head and snout variable and of no diagnostic value;
postocular stripe uninterrupted having dark borders (UMMZ 92754), or
interrupted having pale segment behind eye (TU 13282); other
variations in pattern shown on TU 10170 and 15818; pale stripes on
snout having dark inner borders that join and form acute angle (TU
381), or lacking dark inner borders and having uninterrupted dark line
connecting anterior margins of orbits (TU 13280); other variations in
pattern on snout shown on TU 1232, 1291 and 15819; specimens
representing illustrations of variation in pattern on snout (Fig. 5 d,
e, f) all from same locality, Lewisville, Lafayette County, Arkansas;
contrasting pattern on side of head of dark marks on pale background;
contrasting pattern of dark marks on dorsal surface of limbs; markings
on hind limbs generally larger than those on forelimbs; small or fine
markings of some specimens reducing contrast in pattern (TU 478, 488);
carapace sometimes having few small blackish dots confined to margin
(CNHM 15474, TU 487, 1253, 13266); ventral surface of plastron and
soft parts of body whitish and usually lacking dark markings; small
blackish marks often occurring on flap of carapace, in region of
bridge, or on chin and throat (TU 399, 469, 475, 472, 13281).

Ontogenetic variation in PL/HW, mean PL/HW of specimens having
plastral lengths 7.0 centimeters or less, 4.15, and exceeding 7.0
centimeters, 5.32; ontogenetic variation in CL/CW, mean CL/CW of
specimens having plastral lengths 8.5 centimeters or less, 1.10, and
exceeding 8.5 centimeters, 1.14; mean CL/PCW, 2.12; mean HW/SL, 1.38
(including subspecies _guadalupensis_); mean CL/PL, 1.36.

_Variation._--In 1953, I casually glanced at a hatchling softshell
from the Calcasieu River drainage in the private collection of Mr.
Wilfred T. Neill; the specimen was considered by Neill (1951:15) as
"... an intergradient one (with the _hartwegi-spinifer_ population in
the lower Mississippi drainage)." The hatchling does deviate from
"typical" _pallidus_ in having darkish flecks posteriorly on the
carapace.

I have seen only one adult male (USNM 94457) from the Sabine River
drainage (Orange County, Texas) that shows characteristics of
_guadalupensis_ (white dots on carapace encircled with small black
ocelli); another adult male (USNM 94456) from the same locality
resembles _pallidus_. Those two USNM specimens were mentioned by Neill
(1951:13) as indicating intergradation with "... the mixed
_spinifera-hartwegi-asper_ populations of Louisiana."

Two adult males (SM 2889, Pl. 40, bottom, left, and TCWC 471, Trinity
River drainage) have blackish ocelli surrounding the white dots on the
posterior part of the carapace; two large females (TU 14402, Pl. 40,
bottom, right, plastral length, 17.5 cm., and TU 14417 plastral
length, 21.3 cm., both from the Trinity River) have contrasting
mottled and blotched patterns with white dots visible on the carapace.
These turtles show alliance with _guadalupensis_.

Some individuals from the Brazos River drainage have features
suggesting those that are characteristic of _guadalupensis_.
Hatchlings may have large white dots on the anterior half of the
carapace (USNM 55601). Adult males may have dusky ocelli surrounding
the white dots on the carapace (TU 14169, 14559.1, 14559.2). The
whitish dots, rarely as large as two millimeters, are never so large
as in _guadalupensis_ (three mm. in diameter), and are usually smaller
anteriorly than posteriorly; TU 14169 has white dots approximately the
same size (1.2 mm.) on the anterior half as on the posterior half of
the carapace. The tubercles on adult males are equilateral or
subconical, usually having sharp tips (TU 14348, 14559.1, 14559.2);
the tubercles on large females are subconical, resembling the end of a
bullet, and, in both sexes the tubercles are less conical than those
on specimens of _pallidus_ from farther east.

Three specimens from the Brazos River drainage are particularly
impressive in their alliance with _guadalupensis_. SM 2556, an adult
male, has large white dots that are encircled with black ocelli on the
posterior half of the carapace, but lacks white dots on the anterior
half. TNHC 14068, a hatchling, has small black dots interspersed with
the larger white dots posteriorly. CNHM 46289 has large white spots on
the carapace that are surrounded with two to four black dots;
scattered black dots also intermix with white spots on the surface of
the carapace (less extensive anteriorly).

Color notes taken from a freshly-killed adult male (KU 47121) from the
Brazos River, seven miles below Whitney Dam, Bosque-Hill county line,
Texas, are: Carapace pale brown or tan bordered by black line, having
pale lemon yellow rim; yellowish-cream spots on carapace faintly
surrounded with black stippling; dorsal surface of soft parts of body
olive having black marks and patches of grayish; webbing on limbs
having golden or yellowish hue, brighter distally; interorbital region
brown; black-bordered, postocular stripe orange-cream; snout and side
of head olive having pale areas of orange-cream; iris cream having
black stripe; yellowish at juncture of dark dorsal and pale ventral
coloration with orangish tinge on forelimbs and head; tail pale brown
or tan, flanked by black borders that suffuse laterally into
lemon-yellow; undersurface whitish, pale yellow on neck, bluish-gray
on throat.

_Comparisons._--_T. s. pallidus_ most closely resembles _T. s.
guadalupensis_, but can be distinguished from that subspecies in
having small white tubercles, rarely two millimeters in diameter, on a
pale background, that are not surrounded by blackish ocelli, and are
usually absent, or not conspicuous on the anterior third of the
carapace in adult males; also there are usually no conspicuous white
tubercles or dots on the anterior third of the carapace in hatchlings.
Many adult males of _pallidus_ from the Brazos and some from the
Trinity River drainages often have dusky or black ocelli surrounding
the white dots posteriorly on the carapace; males from these river
systems may be distinguished from _guadalupensis_ in having most, if
not all, white dots on the anterior half of the carapace smaller than
those posteriorly, and a pale brown carapace (in life, usually darker
in _guadalupensis_). _T. s. pallidus_ (and _guadalupensis_) is
distinguished from _emoryi_ in lacking a widened pale rim posteriorly,
and in having small white spots on the anterior half of the carapace.
_T. s. pallidus_ resembles _guadalupensis_ and _emoryi_ in having
white spots on the carapace in adult males. _T. s. pallidus_ differs
from _spinifer_, _hartwegi_ and _asper_ in lacking blackish dots or
ocelli that occur in the center of the carapace. _T. s. pallidus_
resembles _emoryi_ but differs from _guadalupensis_ in lacking black
ocelli surrounding the white spots. _T. s. pallidus_ resembles
_spinifer_, _hartwegi_ and _asper_ but differs from _guadalupensis_
and _emoryi_ in having tubercles along the anterior edge of the
carapace that are conical having sharp tips in males, and conical in
large females.

_T. s. pallidus_ resembles _spinifer_ and _hartwegi_ but differs from
the other subspecies in having a narrow head. _T. s. pallidus_ differs
from _emoryi_ but resembles the other subspecies in having a wider
carapace. _T. s. pallidus_ resembles _emoryi_ and _guadalupensis_, and
differs from the other subspecies in having the carapace widest
farther posterior than one-half the length of the carapace. The snout
of _pallidus_ and _guadalupensis_ is shorter than in _spinifer_ and
_hartwegi_, but longer than in _emoryi_. _T. s. pallidus_ differs from
_asper_ but resembles the other subspecies in having a relatively long
plastron.

_Remarks._--Intergradation of the subspecies _pallidus_ and
_guadalupensis_ is of a clinal nature in which populations
successively show a gradual resemblance to _guadalupensis_ from
western Louisiana and eastern Texas westward to central Texas. Because
the sharpest break in this cline of characters occurs between the
Colorado and Brazos River drainages, the turtles living in the Brazos
River drainage and eastward are referred to _pallidus_, whereas those
in the Colorado River drainage and westward are referred to
_guadalupensis_. For further comments on intergradation between these
two subspecies, see the account of _T. s. guadalupensis_.

Taylor (1935:217-18) reported on some specimens of _Amyda spinifera_
that were obtained by Mr. R. E. McEntyre in "... the spring and summer
of 1926, chiefly about Lewisville, Lafayette County (Arkansas)." Of
the catalog numbers listed by Taylor from Lewisville, 58 (KU,
alcoholic) represent _pallidus_. Three, having the same locality data,
have features that are characteristic of _hartwegi_. KU 2944 (one of
three specimens having this catalog number) is a female having a pale,
mottled and blotched carapace approximately one foot in length; there
are remnants of two dark ocelli, and many widely-scattered,
well-defined dark spots near the periphery of the carapace. KU 2963
(one of three specimens having this catalog number) is an adult male
that has solid, blackish dots on the entire surface of the carapace.
KU 2964 (one of two specimens with this catalog number) is an adult
male that has ocelli approximately five millimeters in diameter on the
carapace (indistinct in center of carapace).

Lewisville is situated in the drainage basin of the Red River and is
approximately eight miles east of the Red River and 30 miles west of
the westernmost tributary of the Ouachita River drainage. _T. s.
pallidus_ occurs in the Red River drainage; _hartwegi_ occurs in the
Ouachita River drainage. Perhaps there is intergradation between
_pallidus_ and _hartwegi_ in the intervening streams. There is no data
to indicate from which river or stream each specimen obtained by
McEntyre came; one would presume that all specimens came from the Red
River drainage. But this is not certain. Certainly the 47 specimens
designated herein as _pallidus_ came from the Red River drainage. I
suspect that KU 2944, 2963 and 2964 were obtained from tributaries of
the Ouachita River drainage.

_T. s. pallidus_ intergrades with the _spinifer-hartwegi_ population
where the Red River joins the Mississippi River in the lower
Mississippi Valley in Louisiana. The majority of 13 juvenal specimens
from the Red River near Shaw, Concordia Parish, Louisiana (USNM
99862-69, 99871-75), resemble _pallidus_ in having inconspicuous white
tubercles on a pale brown carapace. The white tubercles are
conspicuous in USNM 99871. Some specimens have a few small dark dots
confined to the margin of the carapace, as do some "variant"
individuals from well within the geographic range of _pallidus_. USNM
99865 is referred to _hartwegi_ because the carapace is covered with
dark ocelli approximately one millimeter in diameter. Some specimens
from farther west in the Red River drainage are referred to
_hartwegi_. One (USNM 100420) of three from Natchitoches Parish,
Louisiana (TU 5763, USNM 100420-21), having blackish dots on the
carapace, is applicable to _hartwegi_. Of two turtles from Grant
Parish, Louisiana (TU 5647, 12735), only 12735 has dark dots and
ocelli (_hartwegi_). One specimen from Rapides Parish, Louisiana (TU
14040), having dark dots on the entire surface of the carapace, is
referred to _hartwegi_.

Most specimens from the lower Atchafalaya River drainage are referable
to _pallidus_. Eastward, intergradation occurs with the
_spinifer-hartwegi_ population; USNM 100089-90 from Assumption Parish,
near Napoleonville, Louisiana, are referred to _pallidus_. TU 11983,
from Bayou Lafourche, Raceland, La Fourche Parish, and TU 13698.11,
from Bayou Gauche in St. Charles Parish, Louisiana, are juvenal males
that combine the characteristics of _pallidus_ and _hartwegi_; the
carapaces are covered with blackish spots and posteriorly have
distinct whitish dots. The population in the Atchafalaya River more
closely resembles _pallidus_ than it does _hartwegi_ or _spinifer_. In
former times the Atchafalaya River was presumably continuous solely
with the Red River (inhabited by _pallidus_). Now, these two rivers
and the Mississippi River are interconnected in east-central
Louisiana. A large volume of water of the Mississippi drainage is
conveyed to the Gulf of Mexico by the Atchafalaya, and someone has
said that by approximately 1975, unless man interferes, two-thirds to
three-fourths of the total volume of water of the Mississippi River
will be drained by the Atchafalaya. One can expect, therefore, an
increase in the influence of the _hartwegi-spinifer_ population in the
Atchafalaya River drainage.

_Specimens examined._--Total 270, as follows: ARKANSAS: _Lafayette_:
KU 2930-37, 2939-40, 2942, 2944 (two of three specimens bear this
catalog number), 2945-57, 2958 (2), 2959-61, 2963 (two of three
specimens bear this catalog number), 2964 (one of two specimens bears
this catalog number), 2965-73, 2987-89, 3056, Lewisville.

LOUISIANA: _Acadia_: USNM 100151-59, Mermentau River. _Assumption_:
USNM 100089-90, Bayou Lafourche, "near" Napoleonville. _Beauregard_:
TU 1231-32, 1253-55, 1291, 13211, 13266, Sabine River, 8 mi. SW
Merryville. _Bienville_: TU 5649-50, Lake Bistineau. _Caddo_: TU 381,
397-99, 469-72, 474-90, 678, 10170, Caddo Lake: TU 15818-19, Cross
Lake. _Calcasieu_: UMMZ 92754, 5 mi. W Iowa. _Cameron_: TU 1122,
Lacassine Wildlife Refuge. _Concordia_: USNM 99862-64, 99866-69,
99871-75, Red River, "near" Shaw. _De Soto_: SM 2374-75, Wallace
Bayou. _Grant_: TU 5647, Lake Iatt. _Iberville_: USNM 83985, 2 mi. E
Mounds; USNM 100239-41, Grand Lake west of White Castle; USNM 100380,
Plaquemine; USNM 100412, 100414-15, 100419, Spanish Lake, "near" St.
Gabriel. _Jefferson Davis_: Calcasieu River drainage, WTN (no number,
see page 524). _Natchitoches_: TU 5763, Bermuda; USNM 100421, "near"
Natchitoches. _Sabine_: TU 13210, 13212-13, 13265, 13280-82, 13303-06,
Sabine River, 8 mi. SW Negreet. _St. Martin_: USNM 100160, Bayou
Chene; USNM 100650, Atchafalaya. _St. Mary_: USNM 100395-97, 100404,
100409-10, Berwick Bay near Morgan City.

OKLAHOMA: _Atoka_: OU 8966, Rock Creek, 10 mi. E Atoka; OU 8978, McGee
Creek, 7 mi. SW Daisy. _Caddo_: ANSP 100, Washita River, Fort Cobb.
_Choctaw_: OU 27126, Mayhew Creek, 2 mi. NW Boswell. _Comanche_: OU
4130, 4266, 5390, 8333, 12953, 19986, Wichita Mountains Wildlife
Refuge. _Jackson_: OU 13012, 6 mi. E El Dorado. _Kiowa_: CNHM 15474.
_Le Flore_: OU 6791, Kiamichi River, 8 mi. W Arkansas State Line.
_McCurtain_: OU 2149-50, 2152, 2155, 17126-28, 17185, 2 mi. SW
Smithville; USNM 70397, Red River. _Marshall_: KU 40175-76, 50830-31,
50847, OU 27290, 27297, 27562-63, TU 16076 (5), 16175 (6), 16662 (5),
Lake Texoma, 2 mi. E Willis; KU 50832, mouth of Caney Creek, 4 mi. SW
Kingston. _Pushmataha_: OU 2151, 2157; OU 11365, Buffalo Creek, 5 mi.
NW Tuskahoma.

TEXAS: _Archer_: TU 16174, 16668-69, Lake Diversion. _Bell_: SM
5667-69, Nolan Creek. _Bosque_: KU 47121, 7 mi. below Whitney Dam,
Brazos River. _Brazos_: BCB 4436, 10 mi. E College Station; BCB 4437,
17 mi. S College Station; BCB 4438, 4 mi. N Bryan; KU 50833, 4 mi. W
College Station; SM 2556, TCWC 472, Wickson Lake; TCWC 539, Little
Brazos River; TCWC 4692, 8 mi. NE Bryan; TCWC 5121, 2 mi. S College
Station; TCWC no number. _Clay_: TCWC 7258, 8 mi. NW Ringgold,
Montague County; TU 16667.1, 3 mi. W Byers. _Dallas_: MCZ 3987, "near"
Dallas; ANSP 13243, Dallas. _Donley_: ANSP 13440, S of Clarendon.
_Eastland_: KU 3132, Cisco. _Galveston_: TCWC 7251, Alta Loma.
_Harris_: UMMZ 92753, Little Cypress Creek, 1 mi. N Westfield; USNM
94335-36, "near" Houston. _Harrison_: USNM 95386, 16.5 mi. SE Caddo
Lake. _Hill_: TU 14169, Richland Creek, 0.7 mi. W Mertens. _Leon_:
CNHM 46290, 5 mi. W Marquez; TCWC 8994, 8996, 6 mi. NW Normangee.
_Liberty_: TU 14402, 14417, Trinity River, "near" jct. with Big Creek.
_McLennan_: BCB 4665-66, 6 mi. NNE McGregor; SM no number, 2037, 2452,
2552, 2558, 2560, 2640, 5263, 6533, Lake Waco; SM 0185, Middle Bosque
River; SM 2104, 6732, Upper Bosque River; SM 5072, Bull Hide Creek; UI
2399, 1.5 mi. W China Springs; UMMZ 64063, Waco; USNM 55601.
_Madison_: TCWC 471, 517, Twin Lakes. _Montgomery_: TCWC 540, 3 mi. S
Conroe. _Nacogdoches_: TNHC 14112, Legg Creek, 5 mi. S Douglass.
_Orange_: UMMZ 117060, 3 mi. S Orange; USNM 94456-57, Orange.
_Randall_: TTC 576, Palo Duro Canyon, 15 mi. SE Canyon. _Shackelford_:
TU 14547, Clear Fork Brazos River, Fort Griffin State Park.
_Somervell_: TCWC 8995, TU 14559 (4), Brazos River, 5-6 mi. E Glen
Rose. _Trinity_: SM 2889, Groveton. _Walker_: TNHC 20829, 5 mi. E New
Waverly. _Waller_: TNHC 14068, 2.7 mi. E Brazos River on US 90.
_Williamson_: MCZ 1627 (2); TU 14348, San Gabriel River, 6.5 mi. E
Georgetown. _County unknown_: ANSP 13448, Wichita River; USNM 7640,
Brazos River.

_Records in the literature._--LOUISIANA: _Cameron_: Sabine Refuge
(Cagle and Chaney, 1950:386).

OKLAHOMA: _Le Flore_: 6 mi. W Page. _McCurtain_: 14 mi. SE Broken Bow
(Trowbridge, 1937:301).

TEXAS: _Bosque_: Bosque River, "near" Valley Mills (Strecker, 1928:6).
_Harris_: Addicks (Brown, 1950:250). _Henderson_: Cedar Creek
(Strecker, 1926a:7). _Jefferson_: 12 mi. SW Port Arthur (Guidry,
1953:56). _Liberty_: Daisetta (Brown, _loc. cit._); San Jacinto River
(Strecker, 1915:15). _McLennan_: "near" Crawford (Brown, _loc. cit._).
_Orange_: 1 mi. N Bridge City (Guidry, _loc. cit._). _Tarrant_:
Trinity River, Fort Worth (Stejneger, 1944:66). _Taylor_: Abilene
(KKA). _Tyler_: Colmisneil (Siebenrock, 1909:603). _Walker_: 6 mi. E
Huntsville (TCWC 329, listed in card file). _Wheeler_: 5 mi. N Wheeler
(Brown, _loc cit._).

=Trionyx ater= Webb and Legler

Black Softshell

_Trionyx ater_ Webb and Legler, Univ. Kansas Sci. Bull., 40:21,
pls. 1 and 2, 1960, April 20.

_Type._--Holotype, KU 46903, alcoholic female; obtained 16 km. S
Cuatro Ciénegas, Coahuila, México, by John M. Legler (and party),
September 6, 1958.

_Range._--Basin of Cuatro Ciénegas, central Coahuila, Mexico (see map,
Fig. 22).

_Diagnosis._--Posterior margin of carapace of some females having fine
corrugations, edge often ragged, and no pale outer margin; septal
ridges reduced in adult males; over-all dorsal coloration (in
preservative) dark, lacking contrasting patterns.

_Description._--Plastral length of adult male, 9.6 centimeters (KU
46911); of largest female, 18.4 centimeters (KU 46903).

Adult male: anterior edge of carapace smooth; septal ridges reduced;
pale outer rim, and small, whitish, dots posteriorly on carapace;
surface of carapace slightly gritty or sandpapery posteriorly; snout
broadened; over-all dorsal coloration dark gray or slate; contrasting
pattern on soft parts of body lacking; ventral surface whitish having
few blackish marks posteriorly on undersurface of carapace.

Females: posterior margin of carapace usually having fine
corrugations; edge of carapace posteriorly often ragged; pale rim of
carapace absent; mottled and blotched pattern not contrasting on
blackish carapace; dorsal surface of soft parts of body dark gray or
slate, lacking contrasting pattern; ventral surface of carapace and
posterior part of plastron usually having many blackish flecks and
markings; tubercles lacking on anterior edge and in center of carapace
posteriorly; septal ridges well developed.

Medial angle of epiplastron (as observed through overlying skin) bent
at angle of approximately 90 degrees. Other osteological characters
presumably as in _spinifer_.

Range in length of plastron (cm.) of 11 females (mean follows
extremes); 10.8-18.4, 15.0; proportional measurements of 12 specimens
(including adult male, mean follows extremes): PL/HW, 4.70-5.43, 4.93;
CL/CW, 1.28-1.43, 1.32; CL/PCW, 1.98-2.42, 2.15; HW/SL, 1.22-1.58,
1.37; CL/PL, 1.29-1.44, 1.36; some females (especially KU 46908) have
noticeably elongate carapaces.

_Variation._--Corrugations best developed on two largest females (KU
46903, 46906), even present on ventral surface of carapace posteriorly
and on dorsal surface of tail; development of corrugations not
ontogenetic phenomenon as posterior margin relatively smooth on KU
46908 (plastral length, 16.0 cm.) but relatively rugose on KU 46909,
which is smaller (plastral length, 13.9 cm.); smallest female (KU
46904) and adult male having posterior margin smooth; smallest female
having indication of pale outer rim and small whitish dots posteriorly
on carapace, and dark, obtusely-angular line, connecting anterior
margins of orbits; blackish marks on ventral surface reduced on KU
46904, 46910, 46912, and UI 43510; UI 43510 (plastral length, 16.3
cm.) resembles _T. s. emoryi_ in having more contrasting mottled
pattern on carapace and limbs, indication of pale outer rim on
carapace, and dark line connecting anterior margins of orbits; ventral
surface of tail and hind limbs often tinged with red.

Color notes from life of young female, topotype (KU 53755) are:
mottled carapace dark brown, pale areas buff; dorsal surface of head
mottled, olive-brown, pale areas buff; iris orange-buff; upper and
lower lips yellow-orange; dorsal surface of limbs olive-brown having
yellow to buff suffusion and small blackish marks; pale areas on
webbing yellow; ventral surface whitish having yellow at margin of
carapace, on neck and limbs.

_Comparisons._--_T. ater_ most closely resembles _T. spinifer_
(especially the subspecies _emoryi_) in having a gritty or
"sandpapery" carapace (reduced, tubercles more scattered), whitish
dots on posterior third of carapace (small females and adult male) and
a dark line connecting anterior margins of orbits (smallest female).
Prior to acquiring the characteristic darkened, dorsal ground color,
the pattern on the head and limbs seems to be that of _T. s. emoryi_.

_T. ater_ resembles _T. muticus_ in having reduced septal ridges in
males, a smooth anterior edge of carapace (especially males), and no
enlarged prominences on the anterior edge of the carapace or
posteriorly in the center of the carapace on large females. _T. ater_
resembles _T. ferox_ in having an over-all dark coloration dorsally
with no contrasting patterns on adults.

_T. ater_ probably is a small species resembling _T. muticus_ and _T.
spinifer emoryi_. The head is wide in _T. ater_, resembling that of
_T. ferox_, and closely approaching that of _T. spinifer emoryi_ and
_T. s. guadalupensis_. _T. ater_ resembles _T. ferox_ and _T. s.
emoryi_ in having a narrow carapace. _T. ater_ resembles _T. s.
emoryi_, _T. s. guadalupensis_ and _T. s. pallidus_, but differs from
_T. muticus_, _T. ferox_ and the other subspecies of _T. spinifer_ in
having the carapace widest farther posterior than one-half the length
of the carapace. _T. ater_ resembles _T. ferox_ and _T. s. emoryi_ in
shortness of snout. The plastron is short in _T. ater_ and most
closely resembles that of _T. s. pallidus_, _T. s. guadalupensis_, and
_T. s. emoryi_.

_Remarks._--_T. ater_ is confined to permanent, clear-water ponds in
the basin of Cuatro Ciénegas. The male and 11 females (KU) were taken
at the type locality (a pond known locally as Tío Candido); the other
female (UI 43510) was taken from a pond approximately seven miles
northward (known locally as Anteojo). _T. spinifer emoryi_ also occurs
in the basin of Cuatro Ciénegas. Males and females of _emoryi_ were
collected in the Río Mesquites (Río Salado drainage) that drains the
basin; two adult males of _emoryi_ were taken from the clear-water
ponds--one from the type locality of _ater_ (KU 46907), and the other
(KU 53757) from a pond (known locally as El Mojarral) from which no
_ater_ were obtained. This demonstrated sympatry indicates that the
two kinds are not conspecific.

However, the nature and frequency of occurrence of characters of _T.
ater_, suggest that it is subspecifically related to _T. spinifer_--in
effect, a darkened race of _T. s. emoryi_. The diagnostic characters
of fine corrugations on the posterior margin of the carapace and
blackish marks on the ventral surface do not occur on every female of
_ater_. Too, the dorsal coloration of living females (dark brown-buff)
is paler than that of preserved specimens (dark gray-slate).
Furthermore, a hatchling (CNHM 47367) recorded from Cuatro Ciénegas,
Anteojo, is not distinguishable from _emoryi_.

The mention of absence of septal ridges in males of _T. ater_ in the
original description (Webb and Legler, 1960:22) should be amended. The
septal ridges in the only known adult male are reduced; a small,
whitish ridge is present on the medial surface of each nostril, but is
not conspicuous in anterior view. The one adult male of _ater_ is
distinguished from _T. s. emoryi_ principally on the over-all dark,
dorsal coloration with concomitant loss of pattern, the noticeably
broadened snout, and the reduced septal ridges. The last character
mentioned possibly is variable in _ater_ (and in _emoryi_ in this
region) in view of the variation in development of the ridge on four
male _emoryi_ from the basin: well-developed on KU 53757 (Mojarral)
and KU 46907 (Tío Candido); reduced on KU 53752 (Río Mesquites),
resembling development in _ater_; and, reduced on right side only on
KU 53753 (Río Mesquites).

Presumably, the continued erosive action at the headwaters of the Río
Salado has permitted the invasion of this drainage into the formerly
isolated basin of Cuatro Ciénegas. In the basin, however, I know of no
evidence of a direct aquatic contact between the headwater streams and
the isolated, clear-water, ponds. How _emoryi_ entered the ponds is
unknown. Some of the ponds are tapped by small, man-made, irrigation
canals, but, so far as I know, these are not connected to the river.
The ponds have permanent water and are often separated by several
miles of arid environment. Overland dispersal between waterways is
possible in time of flooding. Local residents tell of the infrequent
sale of softshells in Cuatro Ciénegas, which hints at their dispersal
via the agency of man. The underlying gypsum substrate of the valley
has been subjected to considerable erosion; the ponds observed have
deep holes, and small caverns and grottos. There are conflicting
reports concerning subterranean connections between ponds. Possibly
there are underwater connections between some ponds and the headwater
streams of the Río Mesquites. Whatever the dispersal route for
_emoryi_ into the ponds has been, it is strange that the same route
has not been traversed by _ater_, permitting its occurrence in the Río
Mesquites.

On the basis of morphological criteria, I suspect that _ater_ and
_emoryi_ are genetically compatible. Possibly there is only sporadic
entrance of _emoryi_ into the ponds inhabited by _ater_, or the
accessible dispersal routes for _emoryi_ have been relatively recent
and there has been insufficient time for genetic adaptation. _T. ater_
is maintained as a full species because of the occurrence of two
distinct males (KU 46907, _emoryi_, and KU 46911, _ater_) in the same
pond (Tío Candido, the type locality). These two specimens are
contrasted in a photograph accompanying the type description (Webb and
Legler, 1960: Pl. II). The restricted distribution of _ater_, and its
characteristics suggest a relict population derived from a
_ferox_-like ancestor that may be in the process of becoming extinct.

There are two specimens in the CNHM recorded from Cuatro Ciénegas. One
is a female (CNHM 55661) having a plastral length of 19.0 centimeters,
and no specific locality other than Cuatro Ciénegas. I examined this
specimen before I knew of the existence of _ater_, and noted no
unusual features; I have not re-examined the specimen. It is
considered representative of _emoryi_. The second is a hatchling (CNHM
47367) having a plastral length of 3.2 centimeters, recorded from
Cuatro Ciénegas, Anteojo. The carapace is dark tan having small
whitish dots intermixed with a few indistinct, small, blackish specks
posteriorly. The specimen is indistinguishable from _emoryi_.

_Specimens examined._--Total 12, as follows: COAHUILA: KU 46903-06,
46908-12, 53755-56, 16 km. S Cuatro Ciénegas; UI 73510, 5.7 mi. W
Cuatro Ciénegas.

_Records in the literature._--Schmidt and Owens (1944:103) record
_emoryi_ from Cuatro Ciénegas (no museum numbers listed); presumably
their reference is to CNHM 55661.

=Trionyx muticus= Lesueur

Smooth Softshell

_Range._--United States from extreme western Pennsylvania, southern
Minnesota and South Dakota south to the Gulf of Mexico in Alabama, the
western end of the panhandle of Florida, and the eastern half of Texas
(see map, Fig. 22.)

[Illustration: FIG. 22. Geographic distribution of _Trionyx ater_
and _Trionyx muticus_. 1. _T. muticus muticus_. 2. _T. muticus
calvatus_. 3. _T. ater_.]

_Diagnosis._--Septal ridges absent; anterior edge of carapace smooth,
lacking prominences; juvenal pattern of large dusky spots (sometimes
ocellate), or small dusky (not black), dots and short lines; side of
head usually devoid of markings except for pale, usually
uninterrupted, postocular stripe.

Size small; head narrow; snout long; ventral surface of supraoccipital
spine broad proximally, lacking median ridge; foramen magnum evenly
rounded, ovoid; opisthotic-exoccipital spur absent; distal part of
opisthotic wing truncate; lateral condyle of articular surface of
quadrate tapered posteriorly, smaller than medial articular surface;
angle of epiplastron obtuse, approximately 100 degrees; callosity on
epiplastron sometimes covering entire surface; bony bridge wide in
relation to length.

_Description._--Septal ridges absent; external characteristics
variable (see accounts of subspecies); range in length, in
centimeters, of plastron of ten largest specimens of each sex, (mean
follows extremes), males, 11.8-14.0, 12.3; females, 17.7-21.5, 18.9;
ontogenetic variation in PL/HW, mean PL/HW of specimens having
plastral lengths 7.0 centimeters or less, 4.16, ranging from 7.1 to
13.0 centimeters, 5.82, and, exceeding 13.0 centimeters, 7.04; little
ontogenetic variation in CL/CW, mean CL/CW of specimens having
plastral lengths 8.0 centimeters or less, 1.15, and exceeding 8.0
centimeters, 1.16; mean CL/PCW, 1.97; mean HW/SL, 1.22; mean CL/PL,
1.39.

Greatest width of skull usually at level of squamosal (79%); foramen
magnum ovoid; opisthotic-exoccipital spur usually absent (97%); distal
part of opisthotic wing truncate, sometimes visible in dorsal view;
lateral condyle of articular surface of quadrate tapered posteriorly,
smaller than medial articular surface; maxillaries not in contact
above premaxillaries; combination of seven neurals, seven pairs of
pleurals, and contact of seventh pair of pleurals (38%), or eight
neurals, seven pairs of pleurals, and separation of seventh pair of
pleurals (41%); angle of epiplastron obtuse, greater than 90 degrees;
callosities well-developed, frequently on preplastra and epiplastron
of adults.

_Comparisons._--The absence of septal ridges distinguishes _muticus_
from _ferox_, all subspecies of _spinifer_, and _ater_ (ridges are
reduced in males of _ater_). The smooth anterior edge of the carapace
distinguishes _muticus_ from all other American kinds except _ater_
and some individuals of _T. s. emoryi_. _T. muticus_ resembles only
_ater_ and _ferox_ in usually lacking a well-defined, contrasting
pattern of blackish marks on the dorsal surface of the limbs. _T.
muticus_ resembles _ferox_ and differs from _spinifer_ and _ater_ in
lacking a gritty or "sandpapery" carapace on adult males. Adult males
of _T. muticus calvatus_ and some individuals of _T. m. muticus_ from
the Colorado River in Texas further resemble _ferox_ in having
postocular stripes with thick black borders.

_T. muticus_ is the smallest species in North America; the maximum
size of the plastron in adult males is approximately 14.0 centimeters
(16.0 cm. in _spinifer_) and of adult females 21.5 centimeters (31.0
cm. in _spinifer_). Males and females of _muticus_ are sexually mature
at approximately the same size as some _T. s. emoryi_; also, the great
development of the plastral callosities in _muticus_ corresponds to
that in some _emoryi_. The head is narrower in _muticus_ than in
_ferox_ or _spinifer_. The carapaces of specimens of _muticus_
exceeding plastral lengths of 8.0 centimeters are wider than those of
_ferox_, _ater_, _T. s. emoryi_ and _T. s. guadalupensis_ of
corresponding size. _T. muticus_ differs from _ater_ and three
subspecies of _spinifer_ (_pallidus_, _guadalupensis_, _emoryi_) in
having the carapace widest at a plane approximately one-half the
length of the carapace. The snout is longer in _muticus_ than in
_ferox_ and _spinifer_. _T. muticus_ differs from _ferox_ but
resembles _spinifer_ in having a relatively short plastron.

The skulls of _muticus_ differ from those of _ferox_ but resemble
those of _spinifer_ in usually having the skull widest at the level of
the squamosals. Skulls of _muticus_ resemble those of _ferox_ but
differ from those of _spinifer_ in usually lacking a well-developed
opisthotic-exoccipital spur. Skulls of _muticus_ are different from
those of _ferox_ and _spinifer_ in having the 1) ventral surface of
the supraoccipital spine widest proximally, lacking a medial ridge, 2)
foramen magnum ovoid, 3) distal part of opisthotic wing truncate, 4)
lateral condyle of articular surface of quadrate tapered posteriorly,
smaller than medial articular surface, and 5) maxillaries not in
contact above premaxillaries.

Plastrons of _muticus_ differ from those of _spinifer_ and _ferox_ in
having an obtusely-angled epiplastron, relatively large callosities
in adults, and a wide hyo-hypoplastral bridge (in relation to length).

_Remarks._--Agassiz (1857:399) regarded Lesueur's _Trionyx muticus_ as
the type species of the genus _Amyda_ and the only species known to
belong to the genus _Amyda_. Stejneger (1944:7, 9, 12) proposed the
generic name _Euamyda_ as a new name for the North American _Amyda
mutica_ as understood by Agassiz. _Euamyda_ was proposed for use only
if Agassiz's understanding was found to be correct. Actually,
Stejneger thought that the Old World and New World kinds concerned
were congeneric, and that the type species of the genus _Amyda_ was
the Old World species _Amyda javanica_ Schweigger (= _Testudo
cartilaginea_ Boddaert).

If _Trionyx muticus_ Lesueur is considered to be generically distinct
from other soft-shelled turtles, _Euamyda_ Stejneger, 1944, is
available as a generic name with _Trionyx muticus_ Lesueur, 1827, as
the type species (by monotypy).

_Geographical variation._--_Trionyx muticus_ shows no obvious
character gradients; the variation is mostly discontinuous and unlike
that in _T. spinifer_. On the basis of differences in the juvenal
pattern and pattern on head, _T. muticus_ can be divided into two
subspecies.

=Trionyx muticus muticus= Lesueur

Midland Smooth Softshell

Plates 45, 46, and 53

_Trionyx muticus_ Lesueur, Mém. Mus. Hist. Nat. Paris, 15:263,
pl.7, December, 1827.

_Trionyx muticus muticus_ Webb, Publ. Mus. Nat. Hist. Univ. Kansas,
11:520, August 14, 1959.

_Potamochelys? microcephala_ Gray, Proc. Zool. Soc. London, p. 87,
1864.

_Type._--Lectotype, Museum d'Histoire Naturelle, Paris, No. 8813;
dried carapace and plastron; obtained from the Wabash River, New
Harmony, Posey County, Indiana, by C. A. Lesueur in August, 1827 (Pl.
53).

_Range._--Central United States; in the Mississippi River drainage
from extreme western Pennsylvania, southern Minnesota and South Dakota
south to Tennessee, Louisiana and Oklahoma; streams of the Gulf Coast
drainage from the Mississippi River in Louisiana westward into Texas
including the Colorado River drainage (see map, Fig. 22).

_Diagnosis._--Juvenal pattern of dusky dots and usually short lines or
bacilliform marks; ill-defined pale stripes on snout usually evident
just in front of eyes; pale postocular stripe lacking thick, black
borders that are approximately one-half width of pale stripe (except
some in the Colorado River drainage of Texas).

_Description._--Plastral length of smallest hatchling, 2.1 centimeters
(INHS 3458); of largest male, 14.0 centimeters (CNHM 92003); of
largest female, 21.5 centimeters (KU 2308).

Juvenal pattern of dusky, grayish marks lacking sharp margins, and
usually consisting of both small spots and short streaks or dashes,
the former predominating; short streaks or dashes occasionally lacking
(TU 14375, Pl. 45, bottom, left; UMMZ 92751); markings variable in
number, few and widely spaced, or several and closely approximated
(Pl. 45, top, topotypes); pale rim separated from ground color by
ill-defined, dusky margin; pattern on adult males well-defined
resembling that of hatchlings (TU 16172.1, 16173), scarcely
discernable (TU 13294), or absent (TU 1242); mottled and blotched
pattern on carapace usually contrasting in large females.

Pale stripes extending forward from eyes usually not more than half
distance to tip of snout; inner borders of pale stripes on snout
usually absent or dusky and indistinct, occasionally blackish (TU
14606); outer borders of pale stripes darker than inner borders,
usually blackish; pale stripes on snout occasionally absent (CNHM
7845, UMMZ 92665, TU 5989, none of these specimens being large
females); pale postocular stripe having narrow, dusky or blackish
borders (especially UMMZ 92751, TU 14436); pale postocular stripe
usually complete, occasionally interrupted having prominent
dark-bordered anterior segment just behind eye (TU 14416); lower
border of postocular stripe usually in contact with dusky postlabial
line; no other markings on side of head; pattern on dorsal surface of
soft parts of body not contrasting, composed of closely approximated
fine markings that are little darker than background, over-all
coloration pale grayish; occasionally, few larger and more contrasting
markings on hind limbs (UMMZ 92751, TU 14436).

Underparts white, usually lacking markings; occasional dusky markings
on plastral area (UMMZ 110502), dark spots or flecks on undersurface
of carapace (BCB 6043, UMMZ 92666), or markings on throat (UMMZ
95032).

Surface of carapace smooth in adult males; large females lacking
prominences posteriorly in center of carapace or in nuchal region;
anterior edge of carapace smooth in both sexes, but occasionally
having regularly spaced furrows or wrinkles (Fig. 8g).

_Variation._--Short dusky lines and streaks seem to be lacking from
the juvenal pattern on the carapace more often in southern populations
(Gulf Coast drainage of Texas) than in northern populations
(Mississippi River drainage). I have seen one female, KU 48229 (Pl.
46, bottom, left), plastral length 14.5 centimeters that retained a
well-defined juvenal pattern, and lacked a mottled and blotched
pattern.

Color notes from life of 11 turtles, KU 55296-306, (eight adult males,
three immature females) from the Kansas River at Lawrence, Douglas
County, Kansas, are: Buff-yellow rim of carapace, sometimes having
pale orange tinge; dusky, dark brown markings on pale brown or tannish
carapace of males; dark and pale brown mottled and blotched pattern on
carapace of females (smallest specimens having plastral length, 11.0
cm.), many having orangish or buffy hue; soft parts of body brownish
to olive-green dorsally, many having small, blackish marks on hind
limbs; webbing of limbs yellowish; pale orange, some yellow, laterally
at juncture of dark dorsum and pale ventrum (to a lesser extent on
hind limbs); pale orange in some suffusing onto dorsal surface of soft
parts of body; black-bordered postocular stripes in males having
orangish tinge (pattern somewhat obscured in females); whitish ventral
surface in some having pale orangish tinge here and there; many having
dusky, grayish flecking on plastral area and anterior ventral surface
(most intense on 55306 giving appearance of grayish suffusion).

I have seen only three specimens from the Colorado River drainage in
Texas. Two of these (UMMZ 92751, TU 14436) are characterized by much
black pigmentation. A contrasting pattern of relatively large black
marks occurs on the dorsal surface of the soft parts of the body,
especially on the hind limbs, and the pale postocular stripes have
thick black borders. UMMZ 92751, having a plastral length of 5.5
centimeters, has a juvenal pattern of widely-spaced dark dots that
lacks short lines. The other _muticus_ from the Colorado River (CM
3055), a large female 19.0 centimeters in plastral length, has
ill-defined postocular stripes lacking dark borders, although a small
dusky blotch occurs on the right side of the head.

_Comparisons._--_T. m. muticus_ differs from _T. m. calvatus_ in
having pale stripes on the snout, a juvenal pattern of small dusky
spots (usually lacking ocellate spots) and short lines, and a pale
postocular stripe lacking thick, blackish borders (except in some
turtles from the Colorado River system of Texas). One unique
characteristic of _muticus_ is the short, dusky lines in the juvenal
pattern; these marks, however, are occasionally absent.

_Remarks._--_Trionyx muticus_ generally has been considered a distinct
species since its description by Lesueur (1827:263-66, Pl. 7);
Wied-Neuwied (1865:53), at least, questioned the identity of
_muticus_, believing it to be based on a secondary sexual difference
of _T. spiniferus_. Lesueur did not designate a type in the
description, and mentioned that he had seen only three specimens (_op.
cit._:264). Stejneger (1944:17-18) discussed two mounted specimens
(Nos. 787 and 788) in the Natural History Museum at Paris, and
mentioned that No. 787 was designated "... as the type on the printed
label (although presumably not done by Lesueur)." Dr. Jean Guibé (_in
litt._ September 24, 1959) informed me that Nos. 787 and 788 are
numbers without value and correspond, respectively, to catalog numbers
8813 and 8814. In addition, the Museum possesses an alcoholic
specimen, No. 564, obtained by Lesueur from the Wabash River, that
seems to have been acquired by the museum after the publication of the
original description. No. 8813 is regarded as a lectotype.

Gray (1864:87) described the species _microcephalus_ and questionably
included it in the genus _Potamochelys_ Fitzinger, 1843; the locality
was stated as "Sarawak (Wallace)." Gray especially noted the small
elongate head and believed that the acquisition of adult specimens
would prove that it belonged to a new genus. Later, Gray (1869:221)
proposed the generic name _Callinia_ as a new name for _Aspidonectes_
as understood by Agassiz (1857:403). Gray referred _microcephala_ to
_Callinia_ (_op. cit._:214, 222) and recognized also _Amyda mutica_
(_op. cit._:212). Baur (1888:1121) remarked that "_Callinia
microcephala_ Gray, of the British Museum, with the locality Sarawak,
is _Amyda mutica_ Les." The species _microcephalus_ has since been
considered a synonym of _Trionyx muticus_. Schmidt (1953:110)
designated the type locality as New Harmony, Indiana.

Müller (1878:641) listed the species _Trionyx muticus_ from México as
follows: "*b. in Alcohol. Mexico. 1872. [2]." Smith and Taylor
(1950:18, footnote) wrote that the record required confirmation. Webb
and Legler (1960:24) questionably referred this record to the synonomy
of _T. ater_, which resembles _muticus_. _T. muticus_ is not known to
occur in México. According to Dr. Lothar Forcart (_in litt._) of the
Naturhistorische Museum in Basel, Switzerland, only one specimen on
which Müller based his record is extant. My examination of this
specimen reveals that it is a hatchling _T. s. emoryi_, plastral
length 3.5 centimeters, bearing catalog number 1032; there are no
additional data of collection.

Strecker and Williams (1927:16) mentioned one specimen of _muticus_
that was obtained at Christoval, Tom Green County, Texas, and I
presume this is the basis for Pope's mention of this species from Tom
Green County, Texas (1949:319). Although I do not doubt that _T.
muticus_ occurs in Tom Green County, this record possibly is based on
_T. spinifer_ because, 1) there are no specimens of _muticus_ in the
Strecker Museum from Tom Green County, but there is one specimen of
_spinifer_ (SM 3282), and in none of Strecker's publications is there
any mention of _spinifer_ from Tom Green County, and 2) Strecker had,
at least once, misidentified the two species; his record of _muticus_
from Wallace Bayou, Louisiana (Strecker and Frierson, 1926:last page,
no numbers), represents _T. spinifer pallidus_ (SM 2374-75).

_Specimens examined._--Total 261, as follows: ALABAMA: _County
unknown_: USNM 118167, Wheeler Reservoir, Tennessee River.

ARKANSAS: _Franklin_: KU 19459-60, Ozark. _Lafayette_: KU 2938, 3057,
Lewisville. _Lawrence_: CNHM 92003, Imboden; CNHM 92005, Powhatan;
USNM 59214, Black River, Black Rock. _Marion_: TU 14606 (2), White
River at Cotter. _Prairie_: KU 1831, 1868, 1870, 1874-76, 1930-31,
1957-63, 2294-302, 2305-06, 2308-09, 2838-41, 3002, White River,
DeVall's Bluff.

KANSAS: _Barber_: USNM 95185-86, 1 mi. S Lake City. _Doniphan_: KU
1872, 1878, 1964, Doniphan Lake. _Douglas_: KU 2220, 16148, 23230,
40179, 50825-26, 55296-306, Kansas River, Lawrence; KU 45065-66, 1 mi.
N, 1.5 mi. W Lakeview. _Ford_: KU 51516, Ford. _Kearny_: KU 48216, 4
mi. S, 1.5 mi. W Deerfield. _Marshall_: KU 48228, Blue Rapids.
_Pottawatomie_: KU 48229-33, 48238, 2 mi. E Manhattan, Riley County.
_Reno_: USNM 95260, 6 mi. E Turon. _Riley_: KU 46861, 48234-35, 4 mi.
N Manhattan; KU 48236, 2 mi. NE Randolph. _Sedgwick_: UMMZ 95362,
Wichita. _Shawnee_: UMMZ 95366-67, Topeka. _Sumner_: USNM 95415, 3 mi.
SE Oxford. _Washington_: KU 48237, 8 mi. S Hanover. _Woodson_: KU
45064, 1 mi. E, 2 mi. S Neosho Falls. _County unknown_: USNM 51528.

ILLINOIS: _Cass_: INHS 2146, Beardstown. _Coles_: INHS 1965-67, 3 mi.
S Charleston. _Jackson_: INHS 5894, 6.5 mi. N Aldridge, Union County;
UMMZ 81570, Mississippi River. _Jasper_: INHS 2412, Rose Hill.
_Jersey_: INHS 2156-58, Grafton. _Mason_: INHS 2147, Cedar Creek.
_Mercer_: INHS 3458, Keithsburg. _Monroe_: INHS 4088, 3 mi. NE
Columbia. _Morgan_: CNHM 6028, INHS 2148, Meredosia. _Pope_: CNHM 2463
(30), Golconda. _Schuyler_: UI 40-41, Crooked Creek. _Shelby_: INHS
2283, Holliday. _Wabash_: INHS 5228, Mt. Carmel.

INDIANA: _Daviess_: UMMZ 110234, White River, 1.5 mi. W Elnora.
_Jefferson_: USNM 8337, Madison. _Knox_: UMMZ 111880-81, "near" Decker
Chapel. _Posey_: INHS 7278-80, 7447, TTC 798, Wabash River, 2-2.5 mi.
S New Harmony; UMMZ 110598, 8 mi. NW Mt. Vernon.

IOWA: _Allamakee_: UMMZ 92657, 1/4 mi. W Victory, Vernon County,
Wisconsin; UMMZ 92658-64, Mississippi River, "near" Lansing. _Boon_:
UMMZ 92665, Des Moines River at Ledge State Park. _Greene_: UMMZ
92666, 3.5 mi. N Scranton. _Muscatine_: USNM 53521, 54733-34, 54742,
60054-56, Fairport.

LOUISIANA: _Beauregard_: TU 1242, Sabine River, Merryville. _Caddo_:
CNHM 7845, Gayles. _Catahoula_: USNM 113228, Jonesville. _Concordia_:
USNM 99870, Red River, "near" Shaw. _Ouachita_: TU 5989, Monroe.
_Richland_: USNM 100422, Rayville. _Sabine_: TU 13163, 13294, Sabine
River, 8 miles SW Negreet. _St. James_: TU 7543, Vacherie. _St. Mar_:
USNM 100406, Berwick Bay, "near" Morgan City. _Vernon_: KU 41380,
46777, Sabine River NW Burr Ferry.

MINNESOTA: _Hennepin_: AMNH 4761-62, Fort Snelling.

MISSISSIPPI: _Washington:_ USNM 92605, Greenville. _County unknown_:
USNM 115939.

MISSOURI: _Clark_: USNM 59267, 59278, Alexandria. _Daviess_: UMMZ
95505, Grand River, 1 mi. S Jameson. _St. Louis_: SM 2052, St. Louis.
_Wayne_: UMMZ 82823, St. Francis River.

NEBRASKA: _Webster_: UMMZ 89526, Republican River, 2 mi. E Inavale.

OKLAHOMA: _Cleveland_: OU 5480-81, 6473, South Canadian River, 4 mi.
SE Norman. _Hughes_: KU 50845, 4 mi. N Atwood. _Kay_: OU 9741, 8 mi. E
Ponca City. _Le Flore_: OU 2148; OU 27390, Poteau River below Wister
Dam. _Love_: OU 27472, Hickory Creek, 9 mi. E Marietta. _Major_: OU
8597, 7 mi. E Orienta. _Marshall_: KU 50827-29, 50848, 50853, OU
27593-94, TU 16077 (4), Lake Texoma, 2 mi. E Willis. _McIntosh_: OU
8993, 4 mi. W Onapa. _Oklahoma_: OU 10137, Lake Oberholser. _Payne_:
UMMZ 89629, Cimarron River, 3 mi. E Ripley; UMMZ 90002, 19 mi. SE
Stillwater. _Pottawatomie_: OU 25176-83, South Canadian River, 5 mi.
SW Shawnee. _Roger Mills_: OU 12472. _Sequoyah_: OU 9006, Illinois
River, 2 mi. NE Gore. _Tulsa_: UMMZ 95032 (4), Arkansas River at
Tulsa. _Woodward_: CNHM 15472-73; OU 8599-600, 5 mi. E, 1 mi. N
Woodward.

SOUTH DAKOTA: _Yankton_: UMMZ 110499-500, Missouri River at Fort
Randall; UMMZ 110501-02, Missouri River at Yankton.

TENNESSEE: _Benton_: UMMZ 53198, Trotter's Landing. _Lake_: USNM
102677, Reelfoot Lake. _Obion_: USNM 102910, Reelfoot Lake.

TEXAS: _Archer_: TU 16173, Lake Diversion. _Baylor_: TU 16172 (2),
Lake Kemp. _Brazos_: TCWC 7250, Bryan. _Clay_: TCWC 7248-49, 7259-61,
8 mi. NW Ringgold, Montague County; TU 16667, 3 mi. W Byers.
_Grayson_: UI 2419, Lake Texoma. _Gregg_: SM 6685, near Gladewater;
USNM 22629, Sabine River, 5 mi. S Longview. _Liberty_: TU 14416,
14375, Trinity River, "near" jct. with Big Creek. _McLennan_: BCB
6030, 6043, SM 2557, 2561, Lake Waco. _Matagorda_: CM 3055, Colorado
River, Bay City. _San Saba_: TU 14436, San Saba River, 11 mi. NNW San
Saba. _Tarrant_: UMMZ 92750, Worth Lake, Fort Worth. _Wharton_: UMMZ
92751, Colorado River, Wharton.

NO DATA: MCZ 1594 (erroneously recorded from Mobile, Alabama); USNM
029261, 59982.

_Records in the literature._--ARKANSAS: _Garland_: Hot Springs (Combs
and Hurter _in_ Strecker, 1924:47). _Jefferson_: Pine Bluff.
_Pulaski_: Little Rock. _Sebastian_: Fort Smith (Hurter and Strecker,
1909:21).

ILLINOIS: _Adams_: Quincy (Garman _in_ Cahn, 1937:179). _Alexander_:
Horseshoe Lake (Cahn, _loc. cit._); Cairo (Garman _in_ Cahn, _loc.
cit._). _Carroll_: 5 mi. S Savanna (Stejneger, 1944:24). _Clay_:
Louisville. _Clinton_: Carlyle. _Crawford_: Robinson (Cahn, _loc.
cit._). _Cumberland_: Embarrass River (Peters, 1942:183). _Fayette_:
Vandalia. _Gallatin_: Shawneetown (Cahn, _loc. cit._). _Hancock_:
between Warsaw and Hamilton (Stejneger, _op. cit._:23). _Jackson_:
Murphysboro. _Jasper_: Newton. _Marion_: Centralia. _Mason_: Havana.
_Massac_: symbol on map. _Menard_: Petersburg. _Peoria_: Peoria.
_Randolph_: Chester (Cahn, _loc. cit._). _Richland_: Olney (Stejneger,
_loc. cit._). _Rock Island_: Rock Island. _St. Clair_: East St. Louis
(Cahn, _loc. cit._). _Union_: (Cagle, 1942a:199). _White_: Carmi.
_Whiteside_: Sterling (Cahn, _loc. cit._). _Woodford_: Mackinaw Creek
(Garman _in_ Cahn, _loc. cit._).

INDIANA: _Carroll_: "near" Delphi (Agassiz, 1857:400). _Vigo_: Terre
Haute (Blatchley, 1891:22).

IOWA: _Des Moines_: "near" Burlington (Agassiz, 1857:400). _Dubuque_:
Mississippi River, 8 mi. S Dubuque (Goldsmith, 1945:447). _Lee_:
Keokuk (Stejneger, 1944:23).

KANSAS: _Barber_: 5 mi. SE Lake City; Salt River, S of Aetna (Burt,
1935:321). _Cowley_: symbols on map (Smith, 1956:157). _Gray_:
Arkansas River, 1 mi. W Cimarron (Clarke, 1956:215). _Leavenworth_:
Missouri River, Fort Leavenworth (Brumwell, 1951:207-08). _McPherson_:
Lindsborg (Breukelman and Smith, 1946:112). _Pratt_: State Fish
Hatchery, "near" Pratt (Taylor, 1933:269). _Trego_: Wakeeney
(Stejneger, 1944:24).

KENTUCKY: _Fleming_: Fox. _Rowan_: Triplett (Welter and Carr,
1939:130). _County unknown_: Ohio River (Funkhouser, 1925:71).

LOUISIANA: _De Soto_: Bayou Pierre (Strecker and Frierson, 1926:last
page, no numbers).

MINNESOTA: _Houston_: Brownsville (Breckenridge, 1944:183). _Winona_:
Homer (Stejneger, 1944:23).

MISSISSIPPI: _Warren_: Vicksburg (Cook, 1946:185).

MISSOURI: _Jackson_: Fry's Lake (Anderson, 1942:219). _Jefferson_:
Meramec River (Boyer and Heinze, 1934:199). _County unknown_: Osage
River (Agassiz, 1857:400).

NEBRASKA: _Franklin_: 1/2 mi. S Franklin; 1 mi. SE Naponee. _Furnas_:
4 mi. E Cambridge. _Lancaster_: Lincoln. _Nemaha_: Peru. _Thayer_:
(Hudson, 1942:102). _Thomas_: (Smith, 1958:36).

NEW MEXICO: _San Miguel_: Conchos River above Conchos Dam (Shields and
Lindeborg, 1956:120).

OHIO: _Brown_: mouth White Oak Creek, Higginsport. _Muskingum_: "near"
Gaysport. _Pike_: Scioto River in Camp Creek, Newton and Scioto Twps.;
Pike Lake. _Scioto_: Scioto River in Clay and Rush Twps.; Scioto
River, Portsmouth; Scioto River, 3 mi. N Rushtown. _Tuscarawas_:
Tuscarawas River, 2 mi. below Gnadenhutten; "near" Winfield.
_Washington_: Dam No. 2, Muskingum River, northern edge of Marietta;
Ohio River, 4 mi. SE Marietta (Conant, 1951:156, 264).

OKLAHOMA: _Alfalfa_: 6.5 mi. NE Ingersoll. _Comanche_: Camp Boulder,
Wichita National Forest (Ortenburger and Freeman, 1930:188).
_McCurtain_: _Pushmataha_: (Ortenburger, 1927:100).

PENNSYLVANIA: _Allegheny_: Neville Island, Ohio River below Pittsburgh
(Atkinson, 1901:154). _Clarion_: Allegheny River at Foxburg (Netting,
1944:85).

?SOUTH DAKOTA: _County unknown_: Fort Mackenzie, Missouri River, 6-8
mi. below Cedar Island (Stejneger, 1944:15).

TENNESSEE: _Lake_: Mississippi River (Parker, 1948:29). _Pickett_:
Obey River at Eagle Creek Ford (Shoup, Peyton and Gentry, 1941:75).

WISCONSIN: _Crawford_: _Pepin_: Mississippi River (Breckenridge,
1944:183; Pope and Dickinson, 1928:82).

=Trionyx muticus calvatus= Webb

Gulf Coast Smooth Softshell

Plate 47

_Trionyx muticus calvatus_ Webb, Univ. Kansas Publ. Mus. Nat.
Hist., 11:519, 1 fig., 2 pls., August 14, 1959.

_Type._--Holotype, UI 31071, hatchling, sex undetermined, alcoholic;
obtained from Pearl River, Roses Bluff, 14 miles northeast Jackson,
Rankin County, Mississippi, by William F. Childers on August 25, 1952.

_Range._--Southeastern United States from the Florida Parishes of
Louisiana eastward to the western end of the panhandle of Florida;
rivers of the Gulf Coast drainage from the Escambia River drainage,
Florida, westward to Louisiana and Mississippi including the Pearl
River drainage. The eastern extent of geographic range is not known
(see map, Fig. 22).

_Diagnosis._--Juvenal pattern of large circular spots, often ocellate;
no stripes on dorsal surface of snout; pattern on dorsal surface of
limbs of fine markings, not in contrast with ground color; pale
postocular stripes having thick black borders approximately one half
width of pale stripe on adult males.

_Description._--Plastral length of smallest hatchling, 3.0 centimeters
(TU 17301); of largest male, 11.8 centimeters (KU 47118); of largest
female, 18.0 centimeters (TU 13473).

Juvenal pattern of dusky, circular spots, some ocellate, lacking short
lines and streaks; number of spots variable; some spots on carapace of
hatchlings may have maximum diameter of three millimeters (TU 17301);
pale rim of carapace having dusky, ragged, inner border; juvenal
pattern on adult males absent or usually evident, at least posteriorly
(TU 17306.1).

Dorsal surface of snout lacking pale stripes just in front of eyes;
pale postocular stripe having thick, black borders on adult males, but
narrower, dusky or blackish borders on juveniles and large females;
lower border of postocular stripe usually in contact with dusky
postlabial line; no other markings on side of head; pattern on dorsal
surface of soft parts of body of closely approximated, fine markings
that are not in contrast with ground color, over-all coloration
grayish; occasionally few larger and more contrasting markings,
especially on hind limbs and anteriolateral surface of forelimbs.

Underparts whitish, lacking markings, occasional black flecks or dusky
marks posteriorly along ventral edge of carapace (TU 17306.3).

_Comparisons._--_T. m. calvatus_ can be distinguished from _T. m.
muticus_ by the absence of pale stripes on the snout just in front of
the eyes, in having pale postocular stripes that have thick, black
borders on adult males, and in having a juvenal pattern of large,
circular spots that are often ocellate and three millimeters in
diameter (no short lines).

_Remarks._--I have not seen specimens of _calvatus_ from the
Tombigbee-Alabama river drainage; presumably Cook's record (1946:185)
from Lowndes County, Mississippi, represents this subspecies.

It is still not certain that _calvatus_ occurs in streams that drain
into Lake Pontchartrain, Louisiana; TU 17236 from the Amite River that
lacks a diagnostic character is questionably referred to _calvatus_
(Webb, 1959:524). As mentioned previously _T. s. asper_ shows little
evidence of intergradation with _T. spinifer_ in the Mississippi River
drainage; _asper_ is present in streams of the Lake Pontchartrain
drainage. _T. m. calvatus_ presumably shows a corresponding
relationship with _T. m. muticus_ in the Mississippi River drainage.
There are no specimens that indicate intergradation between _calvatus_
and _muticus_; _calvatus_ is expected in streams that drain into Lake
Pontchartrain, Louisiana. Probably _calvatus_ occurs eastward in the
Apalachicola drainage system.

_Specimens examined._--Total, 38 as follows: FLORIDA: _Escambia_: KU
47116, 50852, 50854-55, 50835-36, TU 13473, 16682, 17301, 17302 (2),
Escambia River, 2 mi. E, 1 mi. N Century.

LOUISIANA: _East Baton Rouge_: TU 17236, Amite River, "near" Baton
Rouge. _Washington_: TU 13795, Bogue Chitto River, Enon; TU 17303 (5),
TU 17304 (4), Pearl River, "near" Varnado. _No data_: TU 17305.

MISSISSIPPI: _Lawrence_: KU 47117-19, TU 16956, USNM 7655, Pearl River
within 4 mi. of Monticello; TU 17306 (4), Pearl River, 9 mi. S
Monticello. _Marion_: USNM 95133-34, Pearl River, Columbia. _Perry_:
MSC uncatalogued (3), 3 mi. SE New Augusta. _Rankin_: UI 31071, Pearl
River, Roses Bluff, 14 mi. NE Jackson.

_Records in the literature._--MISSISSIPPI: _Forrest_: no data.
_Jones_: Crawford Bridge. _Lowndes_: Columbus, Lake Park (Cook,
1946:185).

NATURAL HISTORY

Habitat

Most writers who describe the general habitat of soft-shelled turtles
mention large rivers and streams having some current, and large
permanent, quiet bodies of water having soft mud or sand bottoms, but
note the general avoidance of temporary water. The impermanence of water
in the ponds and "charcos" of headwaters of streams may preclude the
presence of softshells from these otherwise suitable habitats.
Seemingly, soft-shelled turtles are not restricted to particular local
situations or microhabitats in a continuous aquatic environment as are
some kinds of fish, which seem to be more or less confined to riffle
areas or deep holes. Certain activities of softshells such as burying
themselves in soft sand in shallow water or seeking crawfish and other
food over a gravel-rock substrate or one that is débris-laden, are best
carried on in different habitats. Repeated observations of turtles that
are probably engaged in a specific activity in a restricted area may
lead to erroneous general conclusions regarding the over-all preference
for a specific habitat. Perhaps this accounts for Conant's statement
(1951:156) that "In the lower portion of the Scioto River [Ohio] it
appears that the present species [_muticus_] is abundant while
_spinifer_ is almost entirely absent."

Cagle (1954:181) wrote that softshells "inhabit the extreme headwaters
and smaller tributaries." Other statements in the literature indicate
the variety in kinds of habitat. In Louisiana, Beyer (1900:44)
mentioned _spinifer_ as abundant "in all inland waters, preferring,
however, such bayous which have sloping and sandy banks upon which
they are fond of sunning themselves." Viosca (1923:41) reported
soft-shelled turtles as characteristic "of the large silt-bearing
rivers ... such as the Pearl, Amite, Mississippi and Atchafalaya."
Cagle and Chaney (1950:386) wrote that _spinifer_ in Louisiana was
found in greatest abundance in streams having some current, but that
individuals were also common in quiet areas; the habitats recorded
were: False River--a lake of clear water supporting an abundance of
submerged vegetation, the shallow ends having mats of water hyacinth;
Lakes Iatt and Bistineau--cypress swamps having clear or muddy water;
Caddo Lake--a large lake having a light oil film on the surface of the
water, and vegetation toward the shore consisting of cattails, water
lilies and water hyacinths, and along the bank of cypress and willow
trees; Caddo Lake Spillway--muddy with swift current; Sabine
River--swift current, traps set in quieter backwater areas or near
cypress logs in river; Lacassine Refuge--traps set in inlets and coves
of ship channel having vegetation of water hyacinth, alligator grass,
and along bank, saw grass, cypress knees and snags. Stejneger
(1944:59) reported _spinifer_ taken in barrow pits in Mississippi.

In Southern Illinois, Cagle (1942:160) recorded _spinifer_ in drainage
ditches (normally having several feet of water and a lush growth of
aquatic vegetation) that connect inland swamps to the Mississippi
flood-plain but dry up periodically, and in Elkville Lake, an
artificial lake having much aquatic vegetation in shallow areas (_op.
cit._:157). Myers (1927:339) recorded a _spinifer_ from Indiana from a
"tiny brook." In east-central Illinois P. W. Smith (1947:39) recorded
_spinifer_ in mud-bottomed dredge ditches, lakes, ponds, small streams
and rivers, whereas _muticus_ was found to prefer rivers having clean,
sandy bottoms and was not taken from lakes or small streams. This
restriction in habitat preference of _muticus_ is again emphasized by
Smith and Minton (1957:346) who wrote that in Illinois and Indiana,
_muticus_ "generally avoids lakes and minor streams." Weed (1923:48),
however, recorded _muticus_ (and _spinifer_) from Meredosia Bay,
Illinois, presumably a broad, shallow, muddy ox-bow lake of the
Illinois River.

In Minnesota, _spinifer_ has been taken from the Mississippi River,
which is described as fairly swift having a fluctuating water level,
sandy islands, mud banks, a bed of pebbles and large boulders, and
abundant crawfish (Breckenridge, 1955:5). In Michigan, Edgren
(1942:180) recorded _spinifer_ from a "very small muck-bottomed lake."
Evans and Roecker (1951:69) recorded _spinifer_ from Long Point, Lake
Ontario, which is a "broad sand spit, straight on the lakeward side
but irregular with wet flats and lagoons on the bayside."

In Kansas, Brumwell (1951:207-08) found "mostly young [_muticus_] ...
in the old ponds left during flood stages of the Missouri River" ...
and _spinifer_ occasionally ... "in the backwaters where stagnant
ponds had been formed." In southcentral Kansas, Burt (1935:321)
reported _muticus_ from "a sandbar at junction of a small creek and
Medicine River" ... and ... a "shallow sand-bottomed, algae-filled
pasture streamlet." The same author reported _spinifer_ from a
"sand-bottomed prairie streamlet" ... and ... "an alga-filled pool
near a stream." Burt (_loc. cit._) remarked that "No ecological
differences in general habitat and field behavior of _mutica_ and
_spinifer_ are evident in Kansas." Clarke (1958:21) observed
_spinifer_ in Long Creek (Osage County, Kansas), which is a winding
stream, characterized by numerous deep holes alternating with rocky
riffles, and having high and wooded banks, and mostly mud bottom but
occasional rock bottom.

Marr (1944:490) mentioned a _spinifer_ that was obtained on the bank
of a small, mud-bottomed stream in the Texas panhandle, and Linsdale
and Gressitt (1937:222) recorded _spinifer_ from irrigation canals in
Baja California.

In southern Florida, _ferox_ occurs in all fresh-water habitats
(Duellman and Schwartz, 1958:272). Carr (1940:107) reported _ferox_ as
widely distributed in streams, lakes, big springs and canals. Judging
from the numbers of turtles, "the larger canals in the Everglades must
represent something like an optimum habitat" (Carr, 1952:417). Wright
and Funkhouser (1915:119) wrote that in the Okefinokee Swamp, _ferox_
was especially abundant where the water is deep and the bottom soft,
and the species was found wherever there were alligators. Deckert
(1918:31) wrote that young _ferox_ were taken in springs and brooks
near Jacksonville, Florida. Marchand (_in_ Carr, 1952:417-19) observed
_ferox_ while water-goggling in Florida and noted that individuals
buried themselves in deep water in white sand, mud or bubbling
mud-sand springs, sometimes where there was vegetation overhead.
Neill (1951:16) collected _ferox_ in marshes, "prairies," flood-plain
lakes, lagoons, ox-bow lakes, mangrove swamps, rivers, creeks,
calcareous spring runs, man-made lakes and lime sinks. The same author
(_loc. cit._) reported taking _agassizi_ (= _asper_) in large muddy
rivers, clear "blackwater" streams, calcareous spring runs, creeks,
marshes, lagoons, ox-bow lakes, flood-plain lakes, lime sinks,
man-made lakes, and smaller ponds. Crenshaw and Hopkins (1955:16),
however, stated that in the area where _T. ferox_ and _T. spinifer
asper_ overlap, "_asper_ is nearly always an inhabitant of fluviatile
situations whereas _ferox_ is equally closely confined to
non-fluviatile lakes and ponds"; in the region of sympatry, Schwartz
(1956:8) reported _ferox_ from "a moderately fast, blackwater stream
[Combahee River, South Carolina]."

Carr (1952:417) wrote that _ferox_ is not uncommon near the mouths of
streams in brackish waters, where the tide must occasionally take it
to sea, and cited Conant, who told of an individual found at sea in
Bahaman waters; Carr (1940:25) listed _ferox_ as occasional in the
marine-littoral, mangrove swamps, as did Neill (1951:16). Neill
(1958:26-27) mentioned his observance of _ferox_ at the mouth of the
Pithlachascotee River, Pasco County, Florida, where the water is
sufficiently saline to favor the growth of oysters, and added that
commercial fishermen had told him that these turtles are sometimes
netted with loggerhead sea turtles (_Caretta_) in the Indian River.
Neill (_op. cit._:5-6) also noted the presence of _ferox_ on Meritt
Island, which supports an extensive saltwater herpetofauna, off the
coast of Brevard County, Florida. Löding (1922:47) recorded _spinifer_
from Fig Island, Mobile County, Alabama, which is probably a marine or
brackish water habitat. Cagle and Chaney (1950:386) obtained one
_spinifer_ in a brackish marsh of the Sabine Wildlife Refuge,
Louisiana; the poor trapping returns here (one _Trionyx_ and one
_Pseudemys_ in 408 trap-hours) suggest that fresh-water species are
not abundant in brackish habitats. Neill (1958:26-27) has summarized
the occurrence of soft-shelled turtles in marine and brackish
habitats.

My own observations indicate a variety of habitat preferences; the
term "relatively clear" refers to waters in which visibility extends
four to six inches below the surface at night using a head-light.

Individuals of _spinifer_ have been taken in large, deep rivers having
a moderate to swift current, relatively clear water, mostly sand and
clay bottoms, and emergent débris intermittent along the shoreline;
the banks may be steep and of mud having a sparse growth of herbs
(Black Warrior River, south of Tuscaloosa, Alabama), or of low
extensive, sandy bars and beaches (Escambia River, near Century,
Florida, Pl. 50, Fig. 1). A juvenile _spinifer_ was taken by hand
among rocks in quiet water behind a rocky shoal in the large,
deep-channeled Ocmulgee River (near Hawkinsville, Georgia). Several
individuals of _spinifer_ were seen in the Flint River (near
Bainbridge, Georgia), which had a swift current in a wide, deep
channel, sandy or sand-silt banks, few brush piles along shore and
many oölitic, submergent snags on an otherwise sandy bottom; the water
was exceedingly clear and permitted water-goggling (this habitat has
been obliterated by a dam on the Apalachicola River). A large female
_spinifer_ was taken on a set line from the bottom of one of several
deep holes (approximately seven feet) that were connected by shallow
areas or riffles (near headwaters of Escambia River--Escambia Creek,
Escambia County, Alabama). Two large females of _spinifer_ (one
escaped) were taken on a trotline set in a large, deep, isolated
barrow pit near the Escambia River (near Century, Florida); there was
no aquatic vegetation, the water was slightly turbid, and the
substrate was of a sand-silt or mud.

In Arkansas, _spinifer_ has been taken in large deep rivers having
relatively clear water, a moderate current, steep banks four to 15
feet high, and a substrate of mud with few rocks (one taken on
trotline, escaped; Black River, near Black Rock, Lawrence County). Two
_spinifer_ were taken (trotline and hoop-net) from a smaller
(approximately 50 feet wide) turbid river having a swift current,
débris along the shoreline, and mud-gravel banks (Petit Jean Creek,
Yell County). Several _spinifer_ and _muticus_ were taken from the
White River (Marion County) having a sand-gravel or bed rock bottom
and clear water; individuals were collected by hand in shallow water
(approximately 3-1/2 feet deep) as they lay on the bottom in the main
channel where the current was moderate to swift or in a quiet-water
side channel having submergent vegetation.

Lake Texoma, an impoundment on the Red River, having a fluctuating
water level with no permanent stand of aquatic vegetation, a mud-rock
or sand-silt bottom, and turbid water (Pl. 49, Fig. 1) is a suitable
habitat for _spinifer_ and _muticus_. _T. spinifer_ is found in large
rivers having relatively clear water, moderate currents, emergent logs
and débris, and mud or sand banks (Little River, McCurtain County,
Oklahoma, Pl. 48, Fig. 1), or small, shallow, turbid creeks having
sand-gravel channels of pools connected by riffle areas (Mayhew Creek,
Choctaw County, Oklahoma).

Three _spinifer_ were taken from the Llano River (near Llano, Texas)
in a period of low water level in hoop-nets set in a large quiet-water
pond about four feet deep and having patches of rushes encroaching
into the water from the shore. The river bed of sand, gravel and large
boulders consisted of narrower, swift-water channels, small pools and
riffles, and large ponds.

Individuals of _T. s. emoryi_ have been taken in large ponds having
little or no current, turbid, deep water, and clay or sand-gravel
banks (Río Purificación, Padilla, Tamaulipas). Two _emoryi_ were
collected from a large pond (Río Sabinas, near Sabinas, Coahuila),
which was connected to an adjoining one by riffle areas and had little
or no current, relatively clear, greenish water, clay or mud banks, a
sand-gravel bottom, and was flanked by brush and large cypress trees.
A few _emoryi_ were trapped in hoop-nets that were set in the Río
Mesquites, a stream in central Coahuila approximately 20 feet wide and
six feet deep, flanked by dense stands of _Phragmites_, and having a
moderate current, relatively clear, pea-green water and a mud-sand
substrate with some gravel; the stream enlarged in some places to form
quiet-water coves (Pl. 48, Fig. 2). One adult male _emoryi_ was taken
from a crystal-clear, dendritic, pond (El Mojarral, near Cuatro
Ciénegas, Coahuila), having shallow areas averaging about two feet but
several deep holes--in one of these at the west end of the pond the
water was being emitted under pressure from an underwater cavern and
"bubbling" at the surface; the vegetation consisted of scattered
patches of water-lilies and stonewort; the bottom was a soft mud-marl,
and in some places was carpeted with shells of small gastropods. This
habitat corresponds to that of the type locality of _T. ater_ (Pl. 49,
Fig. 2); see description in Webb and Legler (1960:26). The water of
the ponds is warm; at 8 p. m. on July 31, 1959, the temperature of the
water at the type locality of _ater_ was 29° C., and the air was 27°
C.

An immature female _spinifer_ was taken on a trotline in a swift,
clear, cold-water habitat having mud banks and an abundance of brush
piles (Little Tennessee River, Monroe County, Tennessee). _T.
spinifer_ occurs also in large ox-bow lakes having relatively clear
water, extensive mats of submerged vegetation, a soft mud bottom, and
several emergent stumps and fallen logs (Lake Concordia, Concordia
Parish, Louisiana); alligator grass and cypress trees encroached to
the shoreline.

Locality data of some individuals of _spinifer_, _hartwegi_, _asper_,
_pallidus_ and _emoryi_ that were examined indicated that turtles were
captured in ponds, bayous, sloughs, lakes, impoundments, rivers and
creeks, indicating habitation of essentially all permanent waters.

A juvenile of _hartwegi_ was seen by Mr. Wendell L. Minckley on a
gravel bar jutting into a small, shallow creek having a mud-gravel
bottom (Carnahan Creek, Pottawatomie County, Kansas); the impounding
of the Big Blue River by the Turtle Creek Dam will obliterate this
habitat. Mr. J. Knox Jones, Jr. reported seeing a large softshell in a
narrow, shallow, clear sandy creek in Holt County, Nebraska.

_T. s. emoryi_ occurs in large rivers having generally turbid waters,
a moderate to swift current and mud or sand bottoms such as the Río
Grande; this habitat corresponds to that of large rivers in the
western parts of the range of _T. s. pallidus_ (Red and Washita) and
_T. s. hartwegi_ (Canadian and Cimarron). These last-named rivers, in
periods of low water level, often have shallow, clear, flowing water
in parts of the river bed. _T. s. emoryi_ has also been taken from
small creeks having bottoms of rocks and large boulders (Black River
Village, Eddy County, New Mexico; field notes of Sydney Anderson and
Kenneth Shain, June 12-14, 1958).

I received a hatchling _T. s. guadalupensis_ that was obtained in a
clear, shallow-water stream (Hondo Creek, Bandera County, Texas, on
April 12, 1958). The larger streams and rivers known to be inhabited
by _guadalupensis_ are generally clear having greenish-tinted waters.
The geographic distribution of _guadalupensis_ indicates that that
subspecies occurs principally in those waters that drain the
limestone-mantled, Edward's Plateau off the Balcones Escarpment; the
headwaters are characterized by clear, calcareous streams having
occasional travertine deposits. It is probably this type of habitat to
which Agassiz's statement (1857:408) of "clear, bold and rocky
streams" refers.

There are a few specimens whose locality data indicate a tolerance of
brackish-water habitats. An adult male _spinifer_ was obtained at
Delacroix Island, St. Bernard Parish, Louisiana, a locality said to
have exceedingly brackish waters (Dr. George H. Bick, St. Mary's
College, Notre Dame, Indiana); this adult male (TU 16170) is unique in
having a mottled and blotched pattern. Another adult male (_spinifer_,
TU 16071) was obtained in shallow water in Lake Pontchartrain at the
mouth of Tchefuncta Creek; the salinity at the time of capture was
recorded as 1.7 (datum from Dr. Royal D. Suttkus, Tulane University),
indicating only slightly brackish water. Two _spinifer_ (USNM
100409-10) and one _muticus_ (USNM 100406) were taken at Berwick Bay,
near Morgan City, St. Mary's Parish, Louisiana; the waters at this
locality are probably brackish. The tolerance of brackish waters
doubtless facilitates the dispersal of these turtles along coastal
marshes and swamps, and into adjacent drainage systems. The greater
number of records in the literature pertaining to _ferox_ suggest that
this species may be more tolerant of brackish and marine waters than
are _spinifer_ or _muticus_.

In summary, _T. ferox_ occurs in all fresh-water habitats, but chiefly
in lentic habitats in the northern part of its range where it and _T. s.
asper_ are sympatric. _T. ferox_ possibly is more tolerant of brackish
and marine waters than are the subspecies of _spinifer_ and _muticus_.

The subspecies of _T. spinifer_ occur in all fresh-water habitats. In
the southern part of the geographic range, which overlaps that of _T.
ferox_, _T. s. asper_ occurs principally in running-water habitats. _T.
s. pallidus_ and _T. s. asper_ are tolerant of brackish-water habitats.
_T. s. guadalupensis_, known at present only from rivers and streams,
occurs principally in river systems that drain the Edward's Plateau of
southcentral Texas. _T. ater_ is confined to crystal-clear ponds in
central Coahuila.

The subspecies _muticus_ occurs in large rivers and streams throughout
its geographic range, but is known from lakes and impoundments
principally in the southern part of its range (the northernmost record
is from Reelfoot Lake, Obion County, Tennessee); there is only one
record of _muticus_ from a small, shallow, headwater creek (Reno County,
Kansas), and only one from a lentic habitat (Meredosia Bay, Illinois) in
the northern part of its range. _T. muticus calvatus_ is known at
present only from rivers and streams.

The seemingly greater restriction of _muticus_ to running-water habitats
suggests less vagility than in _spinifer_ (Netting, 1944:86).

Size and coloration are adaptations to habitat. Soft-shelled turtles of
large size are best adapted to mesic, essentially continuous swampy or
marshy habitats, whereas small size is an adaptation to less continuous,
semi-isolated habitats. A turtle of the maximum size attained by _ferox_
in the habitat of _emoryi_ would, in a general way, probably be more
conspicuous and exposed to its enemies, both in the aquatic environment
and during overland excursions; perhaps the kind and amount of food
would be insufficient. In any event, small size is correlated with the
more arid habitats of the southwest, and large size with mesic ones in
the southeast. _T. ferox_, the largest species, and the smallest
population of _T. spinifer_ (resembling _muticus_) both occur in the
southernmost part of the range of the genus. This situation does not
support the corollary of Bergmann's Rule, that pertains to some groups
of terrestrial reptiles, in which those subspecies occurring farther
north, or in cooler climates during their season of activity, tend to be
smaller.

Within the species _spinifer_, the _emoryi_ group of subspecies are
pallid having whitish dots on the carapace and lack extensive black
pigmentation; these features seem to confer protective coloration on the
inhabitants of arid, essentially sandy or muddy habitats having
sluggish, turbid waters, whereas the more contrasting patterns of the
_spinifer_ group of subspecies eastward seem more suited to existence in
clearer, swifter waters.

The occurrence of the two clines, _spinifer-hartwegi_ and
_pallidus-guadalupensis_, in the species _spinifer_ are notable in that
the former occurs mostly in one large continuous drainage system, that
of the Mississippi, and shows no sharp break in the one character
distinguishing the two subspecies whereas populations composing the
_pallidus-guadalupensis_ cline are separated into several river
drainages, and show a relatively sharp break in several characters at
the Brazos-Colorado river divide. This situation seemingly supports the
thesis that clines are maintained by some sort of parallel gradient in
ecological or geological conditions. It is notable that streams draining
the Edward's Plateau (inhabited by _guadalupensis_) differ in quantity
(more) and quality (especially CO_{3}^{--}, Ca^{++}, and Mg^{++} ions)
of their solutes, and probably pH (higher) from those farther east
(Hubbs, 1957:102). The gross difference in habitats mentioned above
(sandy, turbid, sluggish streams in the west _vs._ clear, swift streams
in the east) may affect the differentiation recognizable in the
_spinifer-hartwegi_ cline.

Daily and Seasonal Activity

_Diurnal Habits_

Softshells bask on débris in the water or on banks close to the water;
basking presumably raises the bodily temperature. In general in the
southeastern and southwestern United States, I have seen softshells
basking only rarely but once saw six at one time close together on logs
in Bowie Creek, Hattiesburg, Mississippi (species undetermined). Surface
(1908:122) saw _spinifer_ in rows on rocks or logs in tributaries of the
Ohio River. Duellman and Schwartz (1958:271-72) stated that _ferox_
basks on banks or beds of aquatic vegetation. Deckert (1918:31)
mentioned large _ferox_ "sunning in shallow water at edge of pond."
Minton (1944:447) wrote that _muticus_ and _spinifer_ sun on steep mud
banks (Wabash River). Cahn (1937:180) stated that _muticus_ (in
Illinois) basks on banks at the water's edge but seldom on logs, and
suggests that _muticus_ is less prone to leave the water than
_spinifer_. According to Carr (1952:438), _muticus_ never basks on
logs or rocks. In Ohio, Conant (1951:159) mentioned _spinifer_ as
occasionally basking upon a log or rock, or sometimes on steep clay
banks of streams. On banks, quick escape is facilitated by directing the
head toward the water, thus eliminating the time that it would take to
turn around on land (Conant, _loc. cit._; Newman, 1906:129). Evermann
and Clark (1920:593) mentioned _spinifer_ as basking on sandy or grassy
shores, and large boulders. Muller (1921:181) wrote that _muticus_ basks
four to ten feet from the water's edge on gently sloping sand and mud
shores of small islands in the Mississippi River (near Fairport, Iowa).
Muller stated that basking usually occurs in the morning, up until 2 p.
m., and that beaches with a northern exposure were preferred; he
observed 37 turtles within a 50-foot stretch of beach. In captivity,
hatchlings bask on wire-mesh supports.

I have frequently observed softshells floating at the surface of the
water, a habit previously mentioned by Surface (1908:122) and Pope
(1949:305, 311). Individuals of _Pseudemys_ and, to a lesser extent,
_Graptemys_ also float at the surface; those kinds of turtles and
softshells at least, often appear at the surface of the water, seemingly
as a result of an inquisitiveness, following repeated disturbances that
cause submergence.

Newman (1906:131) described the active pursuit of food: "They crawl or
swim along the bottom, thrusting their snouts under stones and into
masses of aquatic vegetation, occasionally snapping up a crayfish or
larva that they have succeeded in dislodging. They do not tear up their
food, but swallow it whole, using the forefeet to assist in forcing it
down." Surface (1908:123) suggested that softshells may feed "upon
insects which may be found floating on the water," and I have had
captives take insects from the surface of the water. Carr (1940:107)
also wrote that _ferox_ and numerous gars in the Tamiami Canal, often at
the mouths of the tributary ditches, snap at each other furiously as
floating bits of food are washed in from the Everglades. Another habit
that has been mentioned as an aid in acquiring food (Breckenridge,
1944:186; Conant, 1951:156; Hudson, 1942:101) is burrowing just below
the surface in a soft bottom in shallow water, to ambush passing fish,
or other food. Presumably all kinds of softshells do this in both
shallow and deep water of lakes or rivers having a suitable substrate;
_spinifer_ and _muticus_ have been reported to burrow in shallow waters
(no observations in deep water) by Agassiz (1857:333), Cahn (1937:180,
189), Conant (1951:159) and Weed (1923:48). Marchand (_in_ Carr,
1952:417-19) noted that _ferox_ burrows in deep water, and mentioned
that in areas of bare white sand a group of fish invariably surrounds
them, and one can locate buried softshells by observing these particular
schools of fish. No mention was made of the turtles attempting to catch
the fish. Other associations of soft-shelled turtles and fish have been
described. Kirtland (_in_ DeKay, 1842:7) observed several large bass
that closely followed large numbers of turtles floating at the surface.
Newman (1906:131) reported the observations of fishermen in Lake
Maxinkuckee that large-mouth black bass stay not far away from swimming
softshells; the same author also mentioned the observations of Jacob
Reighard, who suggested that bass may be feeding upon minnows that he
noticed following softshells. Seemingly some sort of commensalistic
relationship exists whereby fish acquire food that is dislodged by
grubbing and scurrying of softshells. Probably food is pursued on
occasion from a buried position, but this habit probably is not executed
specifically for obtaining food. Newman (_op. cit._:129) was of the
opinion that burrowing in shallow water is a habit to facilitate
"warming up."

Marchand (_loc. cit._) also wrote of other notable underwater
observations on _ferox_ in Florida. He commented on this turtle's
inquisitiveness in deep water and unconcern upon being touched or even
upon being handled to some degree. Calf-deep in soft mud, he noted a
turtle that "emerged from the mud of the bottom, headed up toward shore,
circled, and when about three feet above the bottom dived suddenly and
completely disappeared." Marchand wrote that some areas on the bottom
(Crystal Springs), which are rooted up by the burrowing of softshells,
are bare and soft, and assume a characteristic, easily recognized,
appearance.

Cahn (1937:180, 189) stated that the burrowing process consists of
"flipping" the loose sand or silt over the back, whereas Conant
(1951:159) described the process as a rapid lateral movement of the
body. My observations of captives agree essentially with Conant's
observations. The initial movement, directed at a slight angle, is
principally with the forelegs although complemented by lateral movements
of the body. When the turtle is approximately half buried, it makes
rapid lateral movements of the body, which completely bury the turtle
and orient its body in a horizontal position.

_Behavior and Adaptations_

Some characteristics of softshells that are often mentioned in the
literature are: extreme shyness or wariness, ferociousness as captives,
dazzling speed and agility on land and in water, and great dependence on
aquatic environment. Certainly they are wary; and this wariness may
account, in part, for the scarcity of observations of basking, and
statements attesting to their great speed on land. To my mind, their
reported ferociousness and savage disposition as captives is overrated;
of the many softshells that I have collected, only a few attempted to
bite. The extensibility of their long neck does warrant more careful
handling than needs to be employed with other species. Holbrook (_in_
Hay, 1892:145) even wrote that they "will sometime leap up and give a
loud hiss," and Newman (1906:130) wrote that "they hiss violently and
thrust out the head." Wright and Funkhouser (1915:120) reported a
captive _ferox_ that "could jump forward practically its own length." I
have been bitten by individuals of _Kinosternon_, _Sternothaerus_,
_Pseudemys_ and _Graptemys_, and cannot support the contention that
softshells are more prone to bite than those species, a view shared by
LeConte (_in_ DeKay, 1842:7); many softshells on initial capture will
tend to withdraw the head completely for a short time. Newman (_loc.
cit._) also wrote that recently captured specimens exude a thick,
yellow, semi-fluid resembling yolk of an egg from the inguinal glands;
the substance, however, is odorless but "undoubtedly homologous with the
emission of the inguinal glands of the musk and snapping tortoises."
Perhaps there is a difference in aggressiveness associated with
geographic location, the age of the turtle or individual temperament.

Smith (1956:159), referring to _muticus_, wrote that they are the best
swimmers of all fresh-water turtles, and perhaps of any turtles.
Corresponding statements of other authors attesting to their speed and
agility (including _spinifer_ and _ferox_) in water and on land are
based principally on the published comments of Muller (1921:181), who
observed that females disturbed while laying eggs "about fifty feet from
water ... covered the distance faster than a man can run." Cahn
(1937:180) also stated that _muticus_ on a "level, unobstructed sand
beach ... can outrun a man," and (_op. cit._:181) can "capture fish with
ease"; Cahn supported the latter statement by relating his observation
of a _muticus_ that captured a small brook trout in a large tank. Smith
(_op. cit._:162) wrote that _spinifer_ is "said to overtake bass."
Doubtless they are good swimmers and they do scurry rapidly on land.

Published statements relating to the strictly aquatic existence of
softshells especially _muticus_, are based on recognition of "its
drastic adaptations to aquatic existence" (Carr, 1952:428); these
adaptations presumably include pharyngeal respiration and the marked
depression of body form. Pharyngeal respiration was demonstrated for
_muticus_ and _spinifer_ (Gage, 1884; Gage and Gage, 1886), and was
considered the principal type of aquatic respiration (some dermal and
some cloacal) in _Trionyx spinifer asper_ by Dunson (1960). Cloacal
bursae (anal respiration) are lacking in trionychids (Smith and James,
1955:88). Accessory pharyngeal respiration is meaningful in light of the
information furnished by Agassiz (1857:282-83), who found that _Trionyx_
has a smaller lung capacity (weight of body in ounces/capacity of lungs
in cubic inches = 16.9) than do some other genera (_Pseudemys_, 2.8;
_Testudo_, 2.7; _Terrapene_, 1.1); corresponding values for more aquatic
species were _Chelydra_, 9.3 and _Kinosternon_, 16.0. Cahn (1937:181),
however, wrote that he has demonstrated pharyngeal respiration in
individuals of _Pseudemys_, _Chrysemys_ and _Sternothaerus_, and Allen
and Neill (1950:13) suggested that it occurs in _Macroclemys_. More
conclusive data are required to detect a positive correlation between
small lung capacity, pharyngeal respiration, and degree of restriction
to an aquatic habitat.

The depressed, soft-margined carapace of softshells has been mentioned
as an adaptation to facilitate burrowing in soft sand or mud, and more
suited for concealment than for speed in aquatic locomotion (Carr,
1952:429; Smith, 1956:162). Nielsen (1951:264-65), commented that in
various lotic invertebrates, dorsoventral flattening of the body was no
commoner than in lentic invertebrates; he wrote that a dorsoventral
flattening is a disadvantage to an animal in a strong current and is an
adaptation "probably ... not to withstand the current directly, but to
avoid it by seeking shelter in narrow crevices." Probably another aid to
concealment, mentioned by Williams and McDowell (1952:272), is the
plastral hinge.

Concealment of softshells is not enhanced by growths of algae on the
carapace. Proctor (1958:637-38) reported that the common, epizoöphytic
alga of chelonians, _Basicladia_, has never been reported from
_Trionyx_; the same author recorded a large amount of filamentous algae,
principally _Stigeoclonium_, but the algae could be easily wiped from
the turtle, and Vinyard (1955:64) recorded an alga, _Dermatophyton
radians_, attached to the skin of the legs of _Trionyx_. I noted a small
patch of greenish scum growing near the insertion of the neck on a
softshell (_spinifer_ from Lake Texoma); cursory examination by Dr. R.
H. Thompson, disclosed one of the colonial ciliate protozoans
(resembling _Opercularia_) with enmeshed green or blue-green algae.
Evermann and Clark (1920:592) mention a _spinifer_ from Lake
Maxinkuckee, Indiana, having a growth of _Opercularia_, covering the
plastron.

_Movement_

The reported proclivity of softshells for a strictly aquatic existence
has been over-emphasized; they are no more confined to aquatic habitats
than some chelydrids (including kinosternids). In fact, there is a
general parallel in habits between members of the two families, namely,
a tendency toward a bottom-dwelling existence, and a burrowing habit.
The alligator snapping turtle (_Macroclemys_) is probably the most
aquatic fresh-water turtle in the United States. The common snapping
turtle and some kinosternids are known to migrate overland. Kinosternids
and trionychids bask frequently, and trionychids have been observed
moving overland. Cox (1894:50) reported a _spinifer_ attempting to climb
a narrowly-stepped, 12-foot dam on Mud Creek at Ravenna, Nebraska; the
turtle failed after repeated struggles, once reaching a height four
inches shy of the brim before tumbling back into the water. Duellman and
Schwartz (1958:271) commented that adults of _ferox_ are often seen on
roads bordering canals, and informants have told me verbally of similar
observations. Conant (1930:61) reported an individual of _ferox_ that
was "... walking across the main street in Venice [Sarasota County,
Florida]." Softshells will travel overland in search for suitable
nesting sites; Newman (1906:130) wrote that _spinifer_ will climb "steep
railway embankments with considerable ease, in order to reach a sand pit
some fifty yards from the water."

From an analysis of species-composition of large reservoirs and lakes
and their adjacent smaller ponds in southern Illinois, Cagle (1942:162)
concluded that softshells "travel overland far less often than do ..."
other species, but that they are "probably the first to move as the
water level falls." On the basis of further observations in the same
region, Cagle (1944:15) wrote that softshells rarely move overland, and
once trapped in a pool of water, they bury themselves and remain there.
He related instances of several individuals having been dug from dried
mud where the last remnants of a water pool had evaporated and he
concluded that the home range is probably confined to one body of water.
That fluctuations in water level affect the movement of softshells is
suggested by Mr. William E. Brode's comment that a commercial fisherman
trapped numerous softshells in the Pearl River, south of Monticello,
Mississippi, in unbaited hoop-nets in late May and June when the water
level was receding after heavy rains.

The meager data available concerning the aquatic movements of softshells
indicate that individuals wander but little. Breckenridge (1955:6,
table 1) found that among 30 recaptured turtles that had been marked,
the greatest distance traveled was 600 yards over a two-year interval;
after a three-month interval one originally captured 30 miles distant,
moved only 200 yards. The statement of a professional turtle trapper
mentioned by Breckenridge (_loc. cit._) and data previously presented
(see page 436), to the effect that over-trapping results in increasingly
diminished returns, tends to support the idea that there is little
aquatic movement in soft-shelled turtles.

Breckenridge (_loc. cit._) mentioned methods of marking softshells and
found that notching the edge of the carapace with a leather punch was
satisfactory; the notches healed but were discernible as shallow
sinuses. The same author mentioned a tattooing device (mentioned also by
Cagle, 1939:171), but no turtles so marked were ever recognized as
recovered. Tagging with a radioactive isotope and detection with
suitable instruments should prove applicable to turtles (see Karlstrom,
1957).

_Nocturnal Habits_

Anderson (1958:212) wrote that hatchlings (_muticus_) leave nests within
the first three hours after sunset, and are active on the surface of the
sand at night. Muller (1921:183) reported hatchlings (_muticus_) leaving
nests at night or early in the morning. Lagler (1954) stated that
_spinifer_ is nocturnal. To my knowledge there are no other published
statements concerning nocturnal activity of soft-shelled turtles. I have
noted them at night on only four different occasions. In two instances
(Clear Fork Brazos River, Texas, and Lake Concordia, Louisiana), the
turtles were resting immediately below the surface of the water on
submerged branches, as one would expect _Pseudemys_ and _Graptemys_ to
do. Another individual was seen swimming near the surface (Ocmulgee
River, 1-1/2 mi. S Jacksonville, Georgia); this observation possibly
represents nocturnal activity, or inquisitiveness owing to the
disturbances caused by the motor of the boat and/or our head lights. A
final observation tends to support the view of nocturnal habits. My
field notes record at least four softshells collected by hand, and a few
other seen in a shallow (approximately four feet deep), quiet, clear
water side channel of the White River (Cotter, Arkansas); the turtles
were seen resting and slowly moving on the bottom or swimming.

_Seasonal Occurrence_

The length of the season of activity increases with decrease in
latitude. Aquatic species in general have longer periods of activity
than terrestrial species at the same northern temperate latitudes. The
southernmost populations of all species of softshells may be active
throughout the year, assuming temperature to be the limiting factor.

There are few published statements relative to the length of the annual
period of activity; all records refer to _spinifer_. In Lake
Maxinkuckee, northern Indiana, Newman (1906:128) wrote that individuals
were first seen in early April on the lake shore in a weak condition
with neck and legs extended, and were easily captured. Lesueur
(1827:262) wrote that _spinifer_ in Indiana appears toward the end of
April. Observations of Evermann and Clark (1920:592) in Lake
Maxinkuckee, and Butler (1894:224) in east central Indiana concurred in
finding that of all kinds of turtles there, softshells appeared last in
spring and disappeared first in fall. Evermann and Clark found small
softshells, benumbed or dead, along the shore as early as March 18 and
also late in fall. The earliest observation for large softshells was
April 29, and the latest was September 7; Butler found that these
turtles rarely appear before April 15 and sometimes not until May 1.
Cahn (1937:191) stated that softshells in Illinois hibernate toward the
end of October and emerge in May or the latter part of April; the same
author mentioned that in southern Illinois the species might remain
sluggishly active all winter. In Ohio, Conant (1951:160) wrote that
individuals were collected every month from March to October, and one
was even taken in December, 1929, in northwestern Ohio. Wright (1919:8)
mentioned observing softshells on April 20 and September 20 (presumably
these were the earliest and latest observations of them) in Monroe and
Wayne counties, New York. Blatchley (1891:34) listed dates of early and
late activity as March 19 and December 11 for Vigo County, Indiana.
Webster (1936:22) recorded the earliest and latest dates of collection
of _spinifer_ in central Oklahoma as June 10 and November 8.

Moore and Rigney (1942:80) found an individual of _muticus_ under six
inches of ice in water about one foot deep on January 31, 1940 (Cimarron
River, Payne County, Oklahoma).

The published information suggests that the length of the normal annual
period of activity of _spinifer_ in latitudes of about 40° and 43° is
approximately five months, from April into September, depending upon the
weather. There are numerous published statements to the effect that the
period of hibernation is passed under a shallow covering of mud in deep
water. Evermann and Clark (_op. cit._: 593) found a softshell
(presumably in a quiescent state) on September 6 that was "buried up to
its eyes in mud at the edge of Lost Lake." Softshells possibly hibernate
in shallow water or in soft mud flats. Conant (_loc. cit._) found that
captives would not hibernate in a pond in a zoo having a bottom of
leaves.

Food Habits

Previous authors, most of whom allude to published statements preceding
their own, characterize soft-shelled turtles as carnivorous and mention
such food items as crawfish, insects, worms, snails, clams, frogs,
tadpoles, fish, and occasional vegetable matter. Stockwell (1878:403)
wrote that the relative lengths of portions of the digestive tract
indicate "a purely carnivorous diet."

In an examination of the contents of 11 stomachs of _spinifer_ from
Michigan, Lagler (1943:304) found that crawfish (47%) and insects
(52%), principally burrowing mayfly naiads (_Hexagenia_), and
dragonfly naiads, comprised the bulk of the diet with cryptogams,
vegetable débris, snails and fish remains present in small amounts.
Breckenridge (1944:186) wrote that 18 specimens of _spinifer_ in
Minnesota contained 44 per cent crawfish, 29 per cent aquatic insects,
8 per cent fish, and 19 per cent unidentified material. Surface
(1908:123) found crawfish in the only two stomachs of specimens he
examined from Pennsylvania. Penn (1950) summarized the results of
those authors, and estimated that crawfishes comprised 58 per cent
(46% by volume) of the diet of softshells. In Indiana, three stomachs
examined by Newman (1906:131) in late June contained: 1) nine
crawfish, 2) four crawfish, 22 dragonfly naiads, 3) nine dragonfly
naiads, few plant buds. Neill (1951a:765) found crawfishes in the
stomachs of five _spinifer_ from the Savannah River, Georgia. Evermann
and Clark (1920:595) wrote that _spinifer_ in Lake Maxinkuckee feeds
principally on crawfishes. Shockley (1949:257) mentioned bottom
organisms and small fishes as food. Clark and Southall (1920:16)
stated that "Its principal food, to judge from a few specimens
examined, consists of crayfishes."

Cahn (1937:183) wrote that the food of _muticus_ in Illinois consists
principally of crawfish, fish, frogs, tadpoles, larger insect larvae
and nymphs, and aquatic mollusks. The kinds of fish eaten were
_Notropis heterolepis_, _N. spilopterus_, _N. hudsonius_, _Lepomis
machrochirus_, _Morone chrysops_, _Perca flavescens_, _Catostomus
commersonnii_, and _Hypentelium nigricans_; Cahn (_loc. cit._) also
stated that the mollusks eaten by _muticus_ are both gastropods and
small, thin-shelled bivalves. In regard to the feeding habits of
_spinifer_ in Illinois, Cahn (_op. cit._:193) listed the following
items in decreasing order of abundance as revealed by examinations of
stomachs: crawfish, minnows, fry of larger fish, frogs, tadpoles,
earthworms, insects (often beetles), and mollusca (_Pisidium_,
_Viviparus_, planorbids). The kinds of fish mentioned were: _Notropis
heterodon_, _N. heterolepis_, _N. hudsonius_, _Catostomus
commersonnii_, _Lepomis humilis_, _L. macrochirus_, _Semotilus
atromaculatus_, _Notemigonus crysoleucas_, _Umbra limi_, and
_Micropterus salmoides_. Cahn (_loc. cit._) also found the remains of
a six-inch brook trout (_Salvelinus_) in the stomach of a 13-inch
_spinifer_ from Wisconsin.

Agassiz (1857:399) found larvae of neuropterous insects in the stomach
of one specimen of _muticus_, and fragments of _Anodonta_ and
_Paludina_ (= _Campeloma_) in the stomach of one _ferox_. The expanded
crushing surfaces of the jaws in some large individuals of _ferox_ may
be an adaptation to mollusc-feeding (Schmidt and Inger, 1957:36).
Surface (1908:123) found _spinifer_ to have fragments of beetles in
one of two specimens examined, and large quantities of corn in another
from Ohio. Webb and Legler (1960:27) reported 23 chrysomelid beetle
larvae (_Donacia_) in one specimen of _T. ater_. Evermann and Clark
(1920:595) reported several _spinifer_ taken on hooks baited with
grasshoppers in water 14 feet deep in Lake Maxinkuckee, Indiana. Hay
(1892:144) wrote of _muticus_ that "If there are potatoes growing near
the water the turtles find their way to them and devour the stems, of
which they are very fond." Wright and Funkhouser (1915:123) stated
that young _ferox_ in the Okefinokee Swamp feed on fish and frogs, and
according to the natives, larger specimens take waterfowl, a statement
that Smith (1956:159) was probably reiterating when he mentioned that
the diet included "perhaps young birds." Parker (1939:88) wrote that
of two _spinifer_ from Reelfoot Lake, Tennessee, one contained
coleopteran remains, and the other an aquatic beetle and two large
tipulid larvae. Wied-Neuwied (1865:54) wrote that Lesueur found worms,
snails, remains of _Paludina_ (= _Campeloma_), fruits and even hard
nuts in stomachs of _muticus_.

Holbrook (_in_ Hay, 1892:145) mentioned that _spinifer_ feeds on fish
and such reptiles as it can secure. There are no published statements
known to me that report reptiles in the diet of American softshells.
Carr (1952:425) erroneously cited Strecker (1927:9) and attributed "a
young lined snake" to the diet of _T. s. emoryi_; Strecker, however,
referred to _Kinosternon flavescens_. In conjunction with raising
softshells on turtle farms, Mitsukuri (1905:261) mentioned that first
and second year-old turtles (_Trionyx sinensis_) must be transferred
to separate ponds or they will be eaten by adults; perhaps
corresponding cannibalistic tendencies exist in confined, natural
habitats in American softshells.

Captives eat essentially the same things that free-living individuals
do, plus scraps of meat (Strecker, 1927:9; Gloyd, 1928:135; Pope,
1949; Conant, 1951:156, 160). Lagler (1943:303) mentioned a young
_spinifer_ that fed on water fleas (_Daphnia_) and canned fish. Conant
(_op. cit._:160) wrote that no captive was observed to take vegetable
matter.

Food, mostly in intestines, of two adult females of _T. s. emoryi_
collected on June 12-14, 1959, from the Río Grande at Lajitas,
Brewster County, Texas, was examined. One female, KU 51961, contained
little food and mostly plant fragments; because the stomach or
intestine was not full of plant fragments, this food probably was
ingested incidentally to the few insects present. Another female, KU
51955, contained insects, which were identified by Dr. George W.
Byers, Department of Entomology, University of Kansas, as follows: 1)
Coleoptera, Dryopidae, genus _Helichus_, most numerous, 350 to 400
individuals; 2) Coleoptera, Scarabaeidae, genus _Phyllophaga_, one
individual; 3) Odonata, Coenagrionidae, fragments, probably one
individual; 4) Hymenoptera, Sphecidae, subfamily Bembicinae, one
individual; 5) Ephemeroptera; fragments of naiad; and 6) a few plant
seeds, pieces of slender roots, weed stems and a couple of fragments
of tree bark. The scarab and wasp probably fell into the water and
were eaten.

TABLE 6. Kinds of Insects Found in Stomachs and Intestines of 11
Specimens of Trionyx m. muticus (Eight Adult Males and Three
Immature Females, 9.0 to 12.5 cm. in Plastral Length) From Douglas
County, Kansas. Frequency of Occurrence (Approximate Number of
Individual Insects/Number of Stomachs in Which Found) Is Given for
Each Item Listed. Fragments of Insects Represent Adults Unless
Otherwise Noted.

Food from the digestive tracts of 11 specimens of _T. m. muticus_ from
the Kansas River at Lawrence, Douglas County, Kansas, were examined
(Table 6). The turtles (KU 55296-306, eight adult males and three
immature females, ranging in plastral length from 9.0 to 12.5 cm.)
were collected in June, 1958, by Mr. Robert R. Patterson. All turtles
were caught on hook and line in a period of about four or five hours
at dusk. Patterson frequently fished below the bridge at Lawrence and
observed that heads of softshells were often seen there about dusk and
that the turtles seemed to prefer a rather shallow, quiet-water area
of swirls and eddies for feeding. The stomachs, and to a lesser
degree, the intestines, were nearly full. Some turtles contained plant
fragments, principally elm seeds. The kinds of food in this sample
were also identified by Dr. Byers and were mostly insects, the most
frequent item being trichopterans; many of the insects eaten
undoubtedly fell into the water. The remains of spiders were found in
four stomachs and crawfish fragments in five.

Stomachs of two adults of _muticus_ from Lake Texoma, Oklahoma, were
opened. The stomach of one (OU 27593) was full of naiads of the
burrowing mayfly _Hexagenia_; that of the other female (OU 27594)
contained exoskeletal remains of crawfish. The two specimens were
drowned in gill nets between the hours of 11 a. m. and 7 p. m., on
July 10, 1954; the intact condition of the mayfly naiads indicated
recent feeding.

The species of American softshells are mainly carnivorous. The presence
of vegetable matter (mentioned in previous paragraphs) in the digestive
tracts of many specimens and True's statement (1893:152) that
soft-shelled turtles include a variety of vegetable matter in their food
indicates omnivorous habits. Duellman and Schwartz (1958:272) stated
that _ferox_ is omnivorous and Carr (1952:430) made a similar statement
for _spinifer_. The diet seems to be determined by the food supply
available, which may vary seasonally or with adverse conditions such as
flooding; under normal environmental conditions, however, vegetable
matter probably is ingested incidentally to other food. There is no
indication of a preference in food habits according to species and
subspecies. Most of the food seems to be obtained by active foraging
that is triggered primarily by movement of the prey; the sense of smell
is probably secondary.

Reproduction

_Size of males at Sexual Maturity_

Elsewhere (1956:121) I have shown that males of _spinifer_ from Lake
Texoma, Oklahoma, and scattered localities in Texas and Louisiana
are sexually mature when they reach a plastral length of 9.0-10.0
centimeters. Adult males have distinct, convoluted, non-pigmented vasa
deferentia and elongate testes, the maximal measurements of which are
about 10 by 30 millimeters. Testes of hatchlings are approximately 4.0
by 0.4 millimeters (TU 13698.12, plastral length 3.2 cm., measured with
ocular micrometer). I am not aware of seasonal changes in size of the
testes.

In reading the discussion that follows, it is well to remember that
males having the cloaca extending beyond the posterior edge of the
carapace are regarded as sexually mature. As an indication of geographic
variation in _spinifer_, I have listed the measurements of the 10
smallest males for only those subspecies of which there are numerous
records (Table 7). Corresponding data for _T. muticus muticus_ are also
listed for comparison.

TABLE 7. Size at Sexual Maturity of the 10 Smallest Males of T. m.
muticus and Selected Subspecies of T. spinifer. The Extremes
Precede the Mean (in Parentheses).

========================+=======================
SPECIES AND SUBSPECIES | Plastral length (cm.)
------------------------+-----------------------
_T. s. spinifer_ | 8.8-10.3 (9.6)
_T. s. hartwegi_ | 9.6-10.5 (10.2)
_T. s. pallidus_ | 9.1-11.2 (10.5)
_T. s. guadalupensis_ | 9.3-10.8 (10.1)
_T. s. emoryi_ | 8.2-9.0 (8.8)
_T. m. muticus_ | 8.2-9.2 (8.7)
------------------------+-----------------------

The data indicate that the size at which sexual maturity is attained in
_emoryi_ (about 8.0-9.0 cm.) is less than in any other subspecies of _T.
spinifer_ (about 9.0-10.0 cm.), and, more importantly, corresponds to
that of _T. m. muticus_. Although the mean for _T. s. spinifer_ is
slightly less than in the remaining subspecies, I doubt that there is
any significant difference according to subspecies in the size at which
sexual maturity is attained in the subspecies _spinifer_, _hartwegi_,
_asper_, _pallidus_ and _guadalupensis_. The corresponding size in _T.
m. muticus_ and _T. s. emoryi_ heightens the morphological resemblance
between these forms. The only sexually mature male of _T. ater_, which
morphologically resembles _emoryi_ and _muticus_, is 9.5 centimeters in
plastral length. I do not know the size at which _T. ferox_ attains
sexual maturity. The smallest sexually mature individual examined by me
was 12.0 centimeters; probably _ferox_ attains sexual maturity at a
larger size than _spinifer_ or _muticus_. The relative size of
attainment of sexual maturity in _ferox_, _spinifer_, and _muticus_
corresponds to the maximum size of the three species; _ferox_ is the
largest species and _muticus_ is the smallest (Table 2).

_Size of Females at Sexual Maturity_

Breckenridge (1955:6) wrote that the development of the mottled pattern
"undoubtedly indicates a stage in the attainment of sexual maturity"; I
have mentioned (1956:121) that the mottled pattern is apparent on
females before sexual maturity is attained. To my knowledge females have
no external characters which appear at the time of attainment of sexual
maturity.

Sexually mature individuals of _ferox_ have been described in various
terms: 31-1/4 pounds (Goff and Goff, 1935:156); six pounds, lengths of
carapace 10-1/2 and 13 inches (Hamilton, 1947:209); greatest width of
head 3-1/2 inches (Wright and Funkhouser, 1915:120). A 10-1/2 inch
carapace presumably represents the smallest turtle and corresponds to a
plastron approximately 22.0 centimeters in length. There is no other
information available concerning size at sexual maturity in _T. ferox_.

There is little published information concerning the size at sexual
maturity in _T. spinifer_. Cahn (1937:193) wrote that _spinifer_ in
Illinois "must attain a carapace length of about 24 centimeters
[plastral length approximately 18.0 cm.] before the females become
sexually mature"; this statement is the basis for Smith's mentioning a
length of 9-1/2 inches (1956:162). Evermann and Clark (1920:595)
recorded the lengths of carapace of some females (presumably all adult)
from Lake Maxinkuckee, Indiana, as 11, 11-3/4, 12-1/2, and 13 inches;
the smallest measurement corresponds to a plastral length of
approximately 21.0 centimeters.

The data concerning reproduction presented in succeeding paragraphs is
based principally upon examinations of turtles in the TU collections; I
am indebted to Dr. Fred R. Cagle for permission to dissect these
turtles. Females are regarded as sexually mature when they have oviducal
eggs or corpora lutea or ovarian follicles exceeding 15 millimeters
in diameter. Hatchlings of _spinifer_ have ovaries that measure
approximately 6.0 × 0.3 millimeters, and straight oviducts 0.2
millimeters in width (TU 5988, plastral length 3.5 cm. measured with
ocular micrometer). In the size at which sexual maturity is attained
there seems to be much individual variation as well as geographic
variation.

Females of _T. s. emoryi_ from the Río Grande in the Big Bend region
of Texas are sexually mature when the plastron is approximately 16.0
centimeters (16.2 cm., KU 51960), and are the smallest adult females
of _spinifer_ that I have seen; these females are representative of
the population from which the smallest adult males of _spinifer_ are
known and which is unique in showing sexual differences in coloration.
A female (TU 3697), having a plastral length of 16.0 centimeters,
which was obtained in the Río Grande near Eagle Pass, Texas, in
mid-July, is immature; the ovaries are compact having the largest
follicles 2.5 millimeters in diameter, and the oviduct is wrinkled and
convoluted but only six millimeters wide. Of three females of _emoryi_
from the Pecos River, Terrell County, Texas, having plastrons 17.4,
18.3 and 18.8 centimeters in length and obtained on June 11, the
largest and smallest are immature, and internally resemble TU 3697. TU
14453.2 (18.3 cm.) is sexually mature having large corpora lutea and
enlarged ovarian follicles. KU 53754, from the Río Salado in central
Coahuila, México, having corpora lutea and a plastral length of 20.3
centimeters, is sexually mature.

Females of _T. s. guadalupensis_, measuring 14.5, 15.7, 16.3, 16.5,
16.8, 17.0, 19.0, and 20.0 centimeters in plastral length and obtained
from June to September, are immature. The female measuring 19.0
centimeters indicates the approach of sexual maturity in having
swollen and convoluted oviducts seven to ten millimeters in width, but
compact ovaries having the largest follicles 4.0 millimeters. The
other _guadalupensis_ whose measurements are given above have oviducts
that do not exceed four millimeters in width, and ovarian follicles
that do not exceed two millimeters in diameter. TU 10187, obtained in
July, plastral length 19.5 centimeters, is sexually mature having
corpora lutea and enlarged follicles. Two other _guadalupensis_, 21.5
and 22.0 centimeters (Pl. 12, top), having ovaries with enlarged
ovarian follicles (the largest in one, only 11 mm.) are considered
sexually mature.

Concerning the subspecies _pallidus_, females (all collected in June
or July) measuring 15.7, 16.3, 17.3, 17.5, 18.7, 19.5, 20.8 and 21.3
centimeters in plastral length are immature having solid, compact
ovaries with the largest follicles not exceeding two millimeters in
diameter; oviducts are straight not exceeding three millimeters in
greatest width, except those turtles measuring 17.3 and 21.3
centimeters in which the oviducts are swollen and convoluted and,
respectively, five and eight millimeters in greatest width. The
smallest sexually mature _pallidus_ is 19.8 centimeters in length;
recorded lengths of other adult females are 23.5, 26.8 and 30.5
centimeters.

Of especial interest are three large female _pallidus_, measuring
24.8, 27.5, and 28.0 centimeters, which appear to be immature; two of
these (TU 13303-04) are from the Sabine River, collected in July, and
the other specimen is without data (presumably from the Sabine River).
The oviducts are large, swollen and convoluted, resembling those in
sexually mature individuals. The ovaries, however, are relatively
solid and compact having approximate measurements of 125 × 6
millimeters (TU 13303) and 85 × 10 millimeters (TU 13304), and
follicles not exceeding five millimeters in diameter.

Females of _spinifer_ from the lower Mississippi Valley of Louisiana
having plastral lengths of 15.0, 15.5, 16.7, 17.5, 18.0, 19.5, 20.0,
20.4, and 20.8 centimeters are considered immature; the ovaries are
compact and solid having follicles not exceeding three millimeters in
diameter, and the oviducts, swollen and convoluted in the larger
individuals, do not exceed six millimeters in width. The ovaries of
the specimen 19.5 centimeters in length mentioned immediately above
had been removed prior to my examination; the oviducts, however, were
relatively straight and only five millimeters in width. Three females
23.0, 25.5, and 25.8 centimeters in length are sexually mature. TU
5518, measuring 21.5 centimeters in length and obtained in June,
indicates the onset of sexual maturity in having large convoluted
oviducts, but the ovaries are solid, compact, measuring 85 × 13
millimeters, and the largest follicles are only 4.5 millimeters. A
larger turtle (TU 13080), 24.5 centimeters, obtained in July, has
juvenal ovaries (largest follicles five mm.); the oviducts are
enlarged and convoluted as in adult females.

Of two _T. s. asper_ collected from the Escambia River in June and
July, one 18.0 centimeters in plastral length is immature, whereas the
other, 27.0 centimeters long, is adult. A female _T. s. hartwegi_,
measuring 20.7 centimeters, is adult having enlarged follicles and
corpora lutea (TTC 719, Pl. 36, bottom).

In summary, females of all subspecies of _spinifer_, except some
_emoryi_, may be sexually mature when the plastron is 18.0 to 20.0
centimeters in length; probably all physiologically normal females are
adult when 22.0 centimeters long. In general, females are sexually
mature at a plastral length of approximately 20.0 centimeters, a
measurement that corresponds to a length of carapace of approximately
28.0 centimeters or about 11 inches. Females representative of that
population of _emoryi_ inhabiting the Río Conchos and the Río Grande
in the Big Bend region of Texas are adult when the plastron is
approximately 16.0 centimeters in length, and are thus the smallest
sexually mature females of the species _spinifer_. Oviducts are large
(at least eight mm. in width, undistended), swollen and convoluted prior
to the first ovulation.

Of interest are the large females (for example, TU 13303, plastral
length 28.0 cm.) that seemingly have immature, relatively small, ovaries
(the oviducts are large and convoluted as in adult females). Possibly
such ovaries represent a regression and are in senile turtles, but I am
inclined to believe that the development of these ovaries has been
arrested probably owing to hormonal unbalance, and that they have never
been functional.

The size of adult females of _T. ater_ is unknown but probably
approximates that of _T. spinifer_ or is slightly less. Females of
_ater_ 15.5 and 17.2 centimeters in length are immature; the largest
female, the holotype, is 18.3 centimeters in length, and was not
dissected.

Females of _T. muticus_ are sexually mature when smaller than _T.
spinifer_. Two turtles, 13.8 and 14.0 centimeters in length, have large
convoluted oviducts about 10 millimeters in width and ovarian follicles
nine to twelve millimeters in diameter, and seem to be near sexual
maturity. The smallest sexually mature female (subspecies _muticus_) is
TU 14436, measuring 14.4 centimeters in plastral length and having
oviducal eggs. Recorded lengths of other adult females are 16.3, 16.5,
17.2 (subspecies _muticus_), and 18.0 centimeters (subspecies
_calvatus_). Two females having plastral lengths of 17.5 (subspecies
_muticus_) and 16.0 centimeters (subspecies _calvatus_) seem sexually
immature. These turtles collected in April and May have ovarian
follicles not exceeding three millimeters in diameter.

_Sexual Activity_

Observations by Mitsukuri (1905:263), Conant (1951:160) and Legler
(1955:98), constitute the extent of our knowledge concerning courtship
and copulation. Legler observed a male _spinifer_ and a female _muticus_
in captivity; the male was the aggressor, following at the rear or above
the female, and at times nipping at the anterior part of her carapace.
During these movements, the posterior edge of the female's carapace was
turned up slightly whereas that of the male was turned down; the turtles
frequently surfaced to breathe. Occasionally the female followed the
male. On the bottom the male crawled onto the female's carapace from the
rear, remaining in a somewhat posterior position as described by Conant
(_loc. cit._), and seemingly not clasping the female with his feet.
Copulation probably occurs in this position; Mitsukuri (_loc. cit._)
mentioned that copulation in _Trionyx sinensis_ occurs at the surface of
the water. The male remains in the coital position for approximately 15
seconds and then slowly drifts to one side and swims away. Legler
observed five coital unions in one-half hour, each preceded by courting
movements.

Legler's observations indicate that the courtship patterns of _muticus_
and _spinifer_ are similar, and that interspecific matings are possible.
I have not noted any hybrid.

Risley (1933:689) mentioned differential movements of the sexes of
_Sternothaerus odoratus_ in conjunction with the breeding cycle. Such
movements are revealed by trapping procedures that yield deviations from
the expected 1:1 sex ratio. That differential sexual movements probably
occur in _Trionyx_ is indicated by my trapping 17 males in a group of 19
_spinifer_ in hoop-nets in Lake Texoma in the period June 14-July 12,
1954. On June 24-26, 1959, a field party from the University of Kansas
collected 15 softshells in hoop-nets at the mouth of the Río San Pedro,
near Meoquí, Chihuahua; all turtles were males. On June 17-18, 1959, the
same expedition trapped 11 males in a group of 13 turtles in the Río
Conchos, near Ojinaga, Chihuahua. Earlier, June 12-14, 1959, 39
softshells were trapped in the Río Grande near Lajitas, Brewster County,
Texas. Of these turtles, however, 19 were adult males and 20 were
females; eight females were adult (sexually mature) all having oviducal
eggs (Fig. 23). One of the two females from Ojinaga, KU 51174, is
sexually mature (plastral length, 16.5 cm.) having oviducal eggs; the
other is immature (plastral length, 8.0 cm.). The only softshell taken
on June 21, 1959, 8 mi. N and 16 mi. W Ojinaga, KU 51173 (plastral
length, 16.3 cm.) is a female having oviducal eggs. The two females from
Lake Texoma are immature (plastral lengths, 9.8 and 12.4 cm.).

The results of trapping may indicate that females frequent shallow water
for a short time before the period of deposition of eggs, but disperse
to deep water after such periods or between them. The movements of
immature females probably approximate those of adult males; the absence
of immature females in the Meoquí series, and near absence (only one) in
the Ojinaga series perhaps is due to fortuitous collecting methods or to
slightly different diurnal movements between adult males and immature
females. Females approaching sexual maturity and those sexually mature
but not having oviducal eggs ready for deposition possibly remain
relatively sedentary in deep water; such females possibly represent
those absent in the 13.0-15.9 size group (Fig. 23). Certainly, factors
other than those pertaining to egg deposition may cause mature egg-laden
females to live in shallow water, or explain the deviations from the
expected 1:1 ratio.

[Illustration: FIG. 23. Size distribution of 39 _Trionyx spinifer
emoryi_ (19 males and 20 females) collected in the period June 12
through June 14, 1959, from the Río Grande, near Lajitas, Brewster
County, Texas. Solid squares represent sexually mature specimens.
Females approaching sexual maturity or those not ready for egg
deposition (13.0-15.9 cm. size group) are possibly sedentary in
deep water.]

One of the immature softshells (KU 51979, plastral length, 9.7 cm.) of
the series from Lajitas is considered to be a female. It combines
characteristics of both sexes. It resembles a male in having a carapace
gritty to the touch, in having prominent white dots posteriorly and in
not having a faint mottled and blotched pattern as do females of the
same size. The postocular and postlabial markings are mostly yellow
(female), but a small patch of the postocular stripe near the junction
with the pale ventral coloration laterally is tinted with orange (male);
the morphological characters and secondary sexual difference in
coloration of this series of softshells has been mentioned on page 512.
The tail is short and pyramidal resembling that of a female. Internally,
there are a pair of ovaries and oviducts; KU 51979 is functionally a
female. An over-production of androgens probably is responsible for the
external masculine characteristics (orange color, gritty carapace and
absence of mottling on carapace).

_Deposition of Eggs_

Concerning _T. ferox_, Wright and Funkhouser (1915:122-23) wrote that
deposition of eggs occurred in June and July in the Okefinokee Swamp
on the sandy parts of the islands or in sandy fields in places exposed
to the direct rays of the sun. The same authors recorded a gravid
female taken on June 22 (_op. cit._:120), and a nest with eggs on June
26. Harper (1926:415) reported egg-laying in June in the Okefinokee
Swamp. Goff and Goff (1935:156) found a female in search of a nesting
site crawling toward a cleared area within a hammock at 11 a. m. on
May 19, about 25 yards from the western shore of Lake Griffin,
Florida. Carr (1940:107) stated that eggs in Florida "are laid from
March to July 10. One individual laid her eggs on a block of ice which
we had buried in the sand." Hamilton (1947:209) observed deposition of
eggs near Fort Myers, Florida, in "a sandy roadbed slightly above the
cypress swamp and ditch levels on either side of the road." ... either
in ... "the ruts formed by cars or the slope of the roadbed"; dates of
deposition of eggs recorded are March 30 at 11 a. m. in bright sun,
and March 31 (from context, the date given as March 21 is considered
an error) at 5 p. m. following a heavy rain. The daily temperatures at
the time of Hamilton's observations "averaged 85° F., the first really
warm spell of the season."

Eigenmann (1896:262) reported egg-laying of _spinifer_ in sand and
gravel in June and July at Turkey Lake (= Lake Wawasee), Indiana. A
turtle was seen digging a nest on June 26, and fresh nests of eggs
were found on June 27 and July 9. Hedrick and Holmes (1956:126) wrote
that a clutch of eggs of _spinifer_ in Minnesota was found about ten
inches deep in sand about one foot from the river; a steep gravel bank
was also cited as a favorite nesting site. Surface (1908:123) stated
that eggs of _spinifer_ in Pennsylvania are laid in May, and the young
hatch in August. Gehlbach and Collette (1959:142) found eggs of
_spinifer_ on June 19 on a sand bank 15 feet from the edge of the
Platte River in Nebraska. Breckenridge (1944:187) wrote that
_spinifer_ in Minnesota nests on sandy beaches from June 14 to July 6.
Cahn (1937:193) stated that deposition of eggs in Illinois occurs in
"June or early July: earlier in the southern part of the state, later
in the northern portion." Force (1930:38) mentioned a gravid female
from Oklahoma obtained on May 20. Evermann and Clark (1920:593) were
of the opinion that _spinifer_ began laying about mid-June and
continued until perhaps late July at Lake Maxinkuckee, Indiana; a
female opened on June 14 had oviducal eggs, and the first nest was
found on June 18. Nests were usually at the edge of an abrupt ascent
in sand; one nest was found in black, mucky soil (_op. cit._:595).
Newman (1906:128) wrote that _spinifer_ in the same lake nests later
than the other species of turtles, as a rule not earlier than the
middle of June (but as early as June 10, _op. cit._:132), and rarely
later than the middle of July; he observed deposition of eggs on June
22. Sites of deposition of eggs were mostly in soft sand not more than
six feet from water; other sites found by Newman (_op. cit._:132-33)
were a sandy, abandoned road bed separated from the shore by a strip
of tall grass, a rock pile (the eggs being dropped into crevices and
sand packed around them), among roots of a tree (the eggs being
deposited between the roots and under them in a very irregular
fashion), and in clay "so hard packed that one could scarcely break it
with the fingers." Natural nest sites in hard clay and a rock pile
seem incongruous with nesting habits of softshells. I note that
Newman's study was not begun until 1902 (_op. cit._:127), and it was
that year that the water level of the lake was high, flooding the
surrounding lowlands (Evermann and Clark, 1920:49-53). Perhaps some of
the nests found by Newman were old and not natural because of
conditions resulting from the receding water level.

Newman (_op. cit._:134-35) mentioned that in small sandy areas nests
were frequently in contact and overlapped; he found one nest
containing nine small eggs contiguous with 23 large eggs. Breckenridge
(1944:187) reported a nest of 56 eggs of two slightly differing sizes,
and probably from two females. Evermann and Clark (1920:594)
discovered "probably 10 or 12 nests in a distance of a few yards" and
mentioned one nest containing 25 eggs "that evidently belonged to two
different sets ... In the bottom were 10 eggs that looked old ... and
... separated from them by sand, were 15 other eggs."

Nesting sites of _muticus_ were mentioned by Muller (1921:181) on one
of several small islands having "gently sloping sand and mud shores,
and interior areas of open sand and densely growing willows" in the
Mississippi River, near Fairport, Iowa. The same author wrote that the
egg-laying season is from late June to early July, and that the female
selected a place 10 to 60 feet inland "with an unobstructed view of
the open water." Farther north on the Mississippi River near Dubuque,
Iowa, Goldsmith (1945:447) found that _muticus_ preferred "clean,
somewhat level sandbars and sandy shores free from trash, weeds ...
and exposed to open view." The same species, however, may "make
unsatisfactory nests ... in any place they can find sand, even in the
weeds and bushes ... when the river is high, covering the sandy plots
..." Sometimes nests, which were "seldom nearer than six feet or more
than twenty-five feet from water ...," were submerged by a rise in
water level. In Missouri, Hurter (1911:251) found that individuals of
_muticus_ came "... out on the sandbars in the Mississippi River to
deposit their eggs ... At the end of May up to the middle of June ..."
Cahn (1937:182) wrote that the nesting season of _muticus_ is early
July near Meredosia, Illinois. Anderson (1958:212, Fig. 1) found nests
of _muticus_ along the Pearl River in Louisiana on an open sandbar
(not in gravel, fine sand or silt), whereas nests of _Graptemys_ were
confined to the landward margin of the sandbar.

The onset and length of the breeding season seems to be geared to the
climatic conditions under which the species occurs, and, as would be
expected, begins earlier and lasts longer in southern latitudes than
in northern latitudes. The period of deposition of eggs in _T. ferox_
(Florida) is from late March to mid-July, whereas that of northern
populations of _spinifer_ and _muticus_ (southern Great Lakes region)
is usually from mid-June to mid-July.

Seemingly there is little difference between species in preference of
nesting sites; a sandy substrate is probably preferred. Gravid females
of _ferox_ and _spinifer_ may wander overland some distance and select
places where the view of the water is obstructed by vegetation; both
species may wander little and nest in full view of the water.
Concerning _muticus_, it is of interest that of the many nests
discovered by Anderson (_loc. cit._) on an open sandbar, all were
those of _muticus_ and none was a nest of _spinifer_. The nests of
_muticus_ mentioned by Muller (_loc. cit._) and Goldsmith (_loc.
cit._) were on open sandbars. On June 4, 1953, six clutches of eggs
were found on an open sandbar of the Escambia River, Florida; all
hatchlings from those eggs that were successfully incubated were
_muticus_. On June 1, 1954, three nests were found on an open sandbar
of the same river (Pl. 50); the temperature within the nests at 6:30
a. m. was approximately 25° C. Two nests were dug in a sand substrate
on the level portion of the bar (Pl. 51, Fig. 1). The third clutch of
eggs was deposited in a sand-gravel substrate at the brim of the
incline from the shore (approximately 30 degrees and about five feet
above the water); the eggs of this clutch were arranged rather
symmetrically (Pl. 51, Fig. 2). Unfortunately, most of the eggs from
these three clutches failed to hatch. Although the data are far from
conclusive, I have the impression that _muticus_ limits its sites of
egg deposition to the open regions of sand bars and does not lay
inland where it must traverse vegetated areas unless preferred nesting
sites are submerged or otherwise unsatisfactory. Females of _spinifer_
may utilize open sandbars for deposition of eggs but not areas where
_muticus_ occurs. In areas where both _muticus_ and _spinifer_ occur,
the latter probably lays farther inland or on the landward margins of
sandbars.

Excavation of nests has been observed in _ferox_ (Hamilton, 1947:209),
_muticus_ (Muller, 1921:181-82; Goldsmith, 1945:448), and _spinifer_
(Newman, 1906:132-33; Cahn, 1937:191-92; Breckenridge, 1960:284).
Turtles leaving the water are cautious, usually stopping and extending
the neck to its greatest length, holding the head high, and sometimes
returning to the water for a short time. Depending on the condition of
the substrate and wariness of the female, nest construction may begin
immediately, or several holes may be dug and then abandoned. The
excavation on level ground or a slight incline is made by means of the
hind feet (Muller mentions digging with the forefeet; I agree with
Pope, 1949:321, and Conant, 1951:264, who consider Muller in error);
the forefeet are firmly planted and not moved during the excavation,
deposition of eggs or the filling of the nest cavity. The hind feet
are used alternately; cloacal water may be used to facilitate digging
or to provide a suitable substrate for the eggs. Cahn mentioned that
some sand may be flung four or five feet, and that during the digging
the head is held high. Breckenridge (_loc. cit._) reported that sand
was thrown a distance of ten feet. The nest may be completed in 16
minutes (Cahn, _loc. cit._) or less than 40 minutes (Newman, _loc.
cit._). Breckenridge recorded 17 eggs laid in six minutes, Cahn
recorded 12 eggs laid in eight minutes, and Hamilton recorded four
eggs laid in three minutes. The hind feet are used to arrange the eggs
and are used alternately to fill the nest cavity; sometimes a little
sand is scraped in before all the eggs are deposited. Muller recorded
the nest cavity as five inches in diameter and ten inches deep, the
finished nest appearing "as a small crater ... about a foot in
diameter, or where the surface is covered with pebbles, as a circular
area of clear sand." Goldsmith reported that the nest cavity was six
to nine inches in depth, and that after deposition and filling with
sand "By certain twisting movements with all four legs, she drags the
plastron around over the sand, making a perfect camouflage." Newman
found the nest flask-shaped having a depth of about six inches, and
diameters of about three inches at the bottom and one and one-half
inches in the neck. Hamilton described a flask-shaped nest, the
entrance of which would "barely permit the passage of an egg ... the
bottom, at a depth of five inches, being about the width of a quart
milk bottle." Cahn related that the "hole descended at an angle of
about 60°," and the eggs thus rolled down an inclined plane.

Possibly the nests of _ferox_ and _spinifer_ differ from those of
_muticus_ in being flask-shaped. A nest of _spinifer_ was reported by
Gehlbach and Collette (_loc. cit._) as having a neck three inches
across, a depth of six inches and a width of five inches at the
bottom. The nests of _muticus_ that I discovered on the Escambia River
were not flask-shaped; the eggs were five to seven inches below the
surface. Evermann and Clark (1920:594) reported eggs of _spinifer_
"generally at a depth of four to ten inches," and Breckenridge (_loc.
cit._) found the topmost eggs about five inches below the surface.
There may be behavioral differences between _ferox_ and _spinifer_ and
_muticus_. Hamilton (_loc. cit._) mentioned that _ferox_ proceeded
with its reproductive duties even when he stood only a few yards away.
Muller (_op. cit._:181) found that _muticus_ would run to the water if
disturbed, without completing deposition of eggs; the same behavior
was described by Cahn (_op. cit._:191) for _spinifer_. Newman
(1906:133) wrote that _spinifer_ will abandon nesting activities if
surprised before egg deposition begins, but will wait to cover the
eggs if interrupted while laying eggs. Goldsmith (1945:448) found that
an observer did not disturb females of _muticus_ when they were laying
eggs (females "could be approached and even touched"), but that, in
the presence of an observer, they would scurry toward the water
without covering the eggs and would not return to cover them. Turtles
frightened in the process of the construction of the nests would not
return to complete the original nest. Harper (1926:415) wrote that
_ferox_, after completing nesting activities, will crawl a few feet
from the nest and scuffle up the surface, presumably to decoy
predators that might otherwise destroy the eggs; this observation has
not been corroborated by other authors. Harper (_op. cit._:416)
recorded the observation of Allen Chesser, who says that females,
after egg deposition, often "... bury themselves, before they go ter
the water, an' stay there ten er twelve hours."

_Reproductive Potential_

Estimates of reproductive potentials are subject to variation of one
kind or another. Counts of oviducal eggs or those in nests may be
misleading, as in some individuals one or more eggs may have been
deposited previously. Mitsukuri (1905:263), Newman (1906:135), Muller
(1921:182), and Cahn (1937:183) have mentioned that the number of eggs
per clutch corresponds to the size of the female. Females of northern
populations may have larger clutches than females of the same size
from southern populations.

TABLE 8. Records in the Literature Pertaining to Number and Size
of Eggs of Three American Species of Trionyx.

Additional records of size of clutch are provided by data from dissected
females (Table 9). All females were collected from May through September
from localities south of latitude 36.5°. The number of eggs includes
those in both oviducts, and the number of ovarian follicles those in
both ovaries. The number and range in size of only the largest group of
follicles is listed; in some instances the size of follicles formed a
graded series, and the designation of a group was arbitrary.

TABLE 9. Length, Number of Oviducal Eggs, and Condition of Ovaries
in Adult Females of T. spinifer and T. muticus.

===========+========================+=========+======================
| | | Ovarian follicles
| | | (total)
SPECIES | Size of female | Eggs +---------+------------
| (plastral length, cm.) | (total) | |
| | | Number | Size (mm.)
-----------+------------------------+---------+---------+------------
_muticus_ | 14.4 | 6 | 14 | 15-18
| 16.3 | 9 | 4 | 15-17
| 16.5 | | 3 | 16
| 16.5 | 3 | 4 | 14-18
| 17.2 | | 13 | 14-21
| 27.0 | | 25 | 18-21
-----------+------------------------+---------+---------+------------
_spinifer_ | 16.2 | 7 | 4 | 16-20
| 16.2 | 7 | 5 | 18-20
| 16.2 | 7 | 1 | 18
| 16.3 | 6 | 5 | 16-18
| 16.3 | 4 | 5 | 15-19
| 16.8 | 6 | 1 | 18
| 17.3 | 3 | 2 | 17
| 18.3 | | 13 | 19-20
| 19.5 | | 2 | 17
| 19.8 | | 4 | 20
| 20.7 | | 11 | 15-18
| 21.5 | | 6 | 8-11
| 22.0 | | 13 | 11-14
| 23.5 | 8 | 12 | 20-24
| 25.5 | 11 | several | 18-22
| 25.8 | 13 | ? | 18-21
| 26.8 | 10 | 5 | 18-20
| 30.5 | 13 | 5 | 20-21
| | 16 | 16 | 16-21
| | 11 | 19 | 15-20
| | 17 | 23 | 18-22
| | 17 | 22 | 14-20
| | 8 | 15 | 18-22
-----------+------------------------+---------+---------+------------

Published data (Table 8) indicate that the average number of eggs per
clutch for the three American species is about 20, although the number
of eggs may exceed 30 in _spinifer_ and _muticus_. Except for those of
_ferox_, most of these records are based on observations in northern
latitudes (approximately 40°). My examination of females from southern
latitudes (below 36.5°) reveals no oviducal egg count greater than 17
and an average number of eggs per clutch of 9.6 per _spinifer_ (Table
9); that of _muticus_ is 7.3, as based on data given in Table 9 as
well as on egg-nest counts of 15, 6, 6, 6, 6, 5, 9, 8, and 8. Ovarian
follicles larger than 15 millimeters in diameter are arbitrarily
considered to comprise the next clutch that will be deposited in the
current season. Follicles of this size possibly are retained until the
following year or some may undergo regression; some of the included
follicles may not be representative of the succeeding egg complement.
The average number of follicles of the most enlarged groups is 9.0 for
_spinifer_ and 10.5 for _muticus_. Females in northern latitudes
probably have a greater reproductive potential than those in southern
latitudes if it is assumed that there is only one laying per season
for an individual; the maximum number of eggs laid at any one time
probably does not exceed 35. There is also an indication that larger
females deposit more eggs than smaller females (Table 9). Muller
(1921:184) mentioned two double eggs (each having two yolks) in the
complement of 33, indicating an abnormally large number and excessive
crowding of eggs in the oviducts. Simkins (1925:188) also mentioned
some eggs of a clutch (form and locality unknown) that were five or
six millimeters larger (about 31-32 mm.) than the rest, and which
"invariably bore twins." The largest number of eggs in a single nest
mentioned by Simkins is 22. If the presence of double-yolked eggs is
indicative of crowding of eggs in the oviducts, the egg complements of
22 and 33 indicate the approximate maximal number of eggs per clutch.
In the species _spinifer_, the average size of sexually mature females
is slightly smaller at some places in the south than in the north.
Therefore, smaller clutches are to be expected in the south.

Many of the females collected in June or July contained corpora lutea
four to eight millimeters in diameter in addition to enlarged ovarian
follicles. Presumably the corpora lutea indicate clutches deposited
earlier in the current season, and the enlarged follicles represent
clutches to be deposited in the current season. One female of
_muticus_ (OU 27593) obtained on July 10, contains oviducal eggs,
ovarian follicles 15-17 millimeters in diameter, and corpora lutea of
different sizes that exceed the number of oviducal eggs; possibly this
female was capable of laying three clutches each season. Corpora
lutea, representing ovulation points of eggs in the oviducts, are
approximately eight millimeters in diameter. In order to establish
definitely the reproductive potentials of any species of turtle, it is
desirable to know the approximate size of ovarian follicles that are
retained by sexually inactive females, and the rate of regression of
the corpora lutea. The data suggest that, in southern populations at
least, two and possibly three clutches of eggs are deposited in the
annual breeding season. Mitsukuri (_in_ Cagle, 1950:38) found that _T.
sinensis_ deposited four groups of eggs each season.

It is suggested that the seasonal reproductive potential of northern
populations (averaging about 20 eggs per clutch, and probably one
clutch per season) is less than that for southern populations
(averaging about 10 eggs per clutch, but three clutches per season).
But owing to variation, there may be no great discrepancy between the
actual potentials of northern and southern populations.

_Eggs_

The eggs of _Trionyx_ are white and spherical having a brittle shell.
Some eggs are occasionally abnormal in shape and size; overcrowding of
eggs in the oviducts may result in small, irregular-shaped eggs, or
large double-yolked eggs. Presumably enlargement of the eggs occurs in
the oviducts and within a short period after deposition prior to
complete hardening of the brittle shell; therefore some eggs in the
oviducts are smaller than those in nests.

The data concerning _ferox_ (Table 8) suggest that the maximum size of
eggs is 31 to 32 millimeters, whereas oviducal eggs are slightly
smaller, about 25 to 27 millimeters. Eggs of _spinifer_ from northern
latitudes (most from approximately 40°, Table 8) also vary in size,
oviducal eggs being as small as 22 millimeters in diameter and the
maximal size about 29 millimeters. Average extreme measurements (in
mm.) of oviducal eggs (number of eggs in parentheses) from females
taken in latitudes of 33 degrees or less are: 25 × 29 (11), 29 × 30
(11), 28 × 30 (13), 28 × 30 (10), 29 × 30 (5), 29 × 29 (8), 25 × 26
(17), 29 × 30 (5), and 28 × 29 (8). The average size of these eggs is
slightly larger than the oviducal eggs of which measurements are given
in Table 8, and suggest larger eggs from more southern latitudes. Eggs
of _muticus_ are smaller than those of _spinifer_ (Cahn, 1937:183) or
_ferox_; the average size of eggs from nests found in Iowa and
Illinois is 22 to 23 millimeters (Table 8). Nine oviducal eggs from a
female obtained in Lake Texoma, Oklahoma, averaged 22 × 23
millimeters. The largest eggs of _muticus_ are from the southernmost
locality; eight eggs from a nest found along the Escambia River,
Florida, averaged 26 × 27 millimeters.

In general, the data suggest that at each laying slightly smaller eggs
but larger numbers are laid by females in northern latitudes, whereas
larger but fewer eggs are laid by females from farther south.

_Incubation and Hatching_

Length of the incubation period seems to depend upon conditions of
heat and moisture, and, in general, to be geared to the prevailing
climatic conditions. Goff and Goff (1935:156) artificially incubated
some eggs of _ferox_ at temperatures varying from 82.3 to 89.2° F.,
and found that the incubation period was 64 days. Muller (1921:184)
wrote that the period of incubation of eggs of _muticus_ (natural
nests at temperatures about 90°., _op. cit._:182, and artificial
nests) in Iowa is from 70 to 75 days. Breckenridge (1944:187) stated
that _spinifer_ makes nests in Minnesota from June 14 to July 6, and
cited reports that indicate hatching in September. Hedrick and Holmes
(1956:126) discovered a nest of eggs in Minnesota on September 5; the
eggs were artificially incubated and some hatched on October 29.
Eigenmann (1896:263) found eggs as late as September in northern
Indiana that "contained young which would have been ready to hatch
about a month later." Cahn (1937:193) wrote that _spinifer_ in
Illinois lays in June or early July and that "young-of-the-year are
taken in late August and September." Some recently deposited eggs of
_muticus_ (as indicated by fresh turtle tracks, Pl. 50, Fig. 2) that I
obtained on June 1 were artificially incubated and hatched on August
4, indicating an approximate incubation period of 65 days. Dr. Paul K.
Anderson in the course of field work on the Pearl River, Louisiana
(1958:211), found that eggs collected on June 13 from a nest excavated
three to five days before, hatched on August 15, indicating an
incubation period of approximately 67 days. Eggs collected on May 17
to 25 (three clutches) hatched on August 4 to 6, indicating an
incubation period of approximately 77 days. In any latitude the
incubation period probably is at least 60 days. Eigenmann (_loc.
cit._), however, mentioned empty nests that were found in July; this
indicates early hatching or more probably the action of predators.

In northern latitudes eggs or young turtles may over-winter in the
nest if deposition is late in the season. In northern Indiana Evermann
and Clark (1920:595) found a nest on November 16 that contained
"well-formed young" and believed that the turtles would have wintered
in the nest. Conant (1951:160) was of the opinion that most eggs
probably hatch in early fall, but that some do not hatch until spring.

The hatching of eggs of _muticus_ has been described by Muller
(1921:183). According to him, the forelimbs first emerge through the
shell and enlarge the opening. There is an "egg tooth below the
flexible proboscis" but "it does not seem to be used in escape from
the eggs, and is dropped a week after hatching." Hatchlings burrow
almost straight upward through the sand leaving the egg shell below
the surface and a hole in the sand about an inch in diameter. Muller
found that young turtles emerge from the nests in the night or early
morning and always go downhill probably influenced in their movements
by the open sky and sloping beach. Anderson (1958:212-15) found that
hatchlings of _muticus_ leave nests within the first three hours after
sunset and travel a direct route to the water. He discovered that
hatchlings are active on the surface of the sand at night and
generally show a positive reaction to light (moonlight, flashlight),
whereas, in daytime, there is a negative reaction to bright sunlight
(causing the turtles to bury themselves in sand). Anderson believed
that the positive response to light at night is not correlated with
the water-approach behavior of hatchlings, but that movements to water
are possibly influenced by a negative reaction to dark masses of
environment (such as shadows formed by landward forests).

_Age and Growth_

Goff and Goff (1935:156) found that hatchlings of _ferox_ average 8.82
grams (extremes, 8.50 to 9.25); one of these, UMMZ 76755, is
illustrated in Plate 31. Muller (1921:184) recorded measurements of
five hatchlings of _muticus_; the average measurements (in cm.,
extremes in parentheses) were: length of carapace, 3.54 (3.43 to
3.67); width of carapace, 3.20 (3.10 to 3.25); length of plastron,
2.54 (2.47 to 2.60). I recorded measurements of 32 hatchlings (three
clutches combined) of _muticus_ on August 16; the turtles hatched on
August 4 to 6 from eggs collected along the Pearl River, Louisiana.
The average measurements (in mm., extremes in parentheses) of the 32
turtles were: length of carapace, 41.3 (34.0 to 45.0); width of
carapace, 38.6 (31.0 to 40.0); length of plastron, 30.1 (25.0 to
32.0). These turtles have circular umbilical scars averaging
approximately two millimeters in diameter. The smallest hatchling that
I have seen measures 21.0 millimeters in plastral length (_T. m.
muticus_, INHS 3458). There are no data to indicate a difference in
size of hatchlings among the American species of soft-shelled turtles.
The average plastral length of most hatchlings probably is 28.0 to
30.0 millimeters.

Owing to the lack of a horny epidermal covering of the carapace and
plastron, soft-shelled turtles are not so well suited to studies of
age and growth as are the "hard-shelled" species, which have visible
impressions of growth annuli on the epidermal scutes. Mattox
(1936:255) found annular rings in the long bones of specimens of
_Chrysemys_ and suggested that it is tenable to correlate the number
of rings with the age of the turtle.

Mitsukuri (1905:265) reported that in hatchlings of _Trionyx sinensis_
the length of the carapace averages 2.7 centimeters (hatchlings of
_sinensis_ seem to average smaller than any American species), and
that the average length of carapace (cm.) at the end of the first year
is 4.5, second year 10.5, third year 12.5, fourth year 16.0, and end
of fifth year 17.5; he stated also that females of _sinensis_ are
sexually mature in their sixth year. Breckenridge (1955:7-9) computed
a growth curve based on 11 recaptures of females of _spinifer_ in
Minnesota; his data on rate of growth for the first five years do not
differ appreciably from those of Mitsukuri. As most females of
_spinifer_ are sexually mature when the carapace is about 11 inches
long, the age at sexual maturity is approximately 12 years according
to Breckenridge (_op. cit._:8, Fig. 4). The discrepancy in age of
females at the size of attainment of sexual maturity (Mitsukuri--six
years; Breckenridge--12 years) is, in part, rectified by the fact that
_Trionyx sinensis_ probably is a smaller species. Also, Breckenridge's
computation of the growth curve is based on continuously decreasing
increments of growth and seemingly eliminates consideration of the
probable marked decrease in rate of growth that occurs when sexual
maturity is attained--a phenomenon noted in other species of turtles.
I think that increments of growth of immature turtles are, on the
average, larger than those of sexually mature turtles. Judging from
these criteria, the age of a female of _spinifer_ at sexual maturity
is less than 12 years, and turtles having carapaces 17 to 18 inches in
length (maximal size for _spinifer_) would be older than 53 years
(_op. cit._:9). Occasional individuals, however, may greatly exceed
the usual growth rate in which event large adults may be younger than
50 years.

Females of _muticus_ are sexually mature when the plastron is 14.0 to
16.0 centimeters long, which corresponds to a carapace 19.6 to 22.4
centimeters (about 7-3/4 to 8-3/4 inches) long (average CL/PL
approximately 1.4, see Fig. 13). The smaller adult females probably
mature sexually in their sixth year, but most probably do so when
seven years old. Accordingly, some _T. spinifer emoryi_, which are
sexually mature at a plastral length of 16.0 centimeters, are also
sexually mature in their seventh year, whereas most _spinifer_
(sexually mature at a plastral length of 18.0 to 20.0 cm.,
corresponding to a length of carapace of 25.2 to 28.0 cm. or about 10
to 11 inches) probably become sexually mature in their ninth year, and
some when eight years old. Most males of _spinifer_ are sexually
mature when the plastron is 9.0 to 10.0 centimeters long (length of
carapace 12.6 to 14.0 cm. or 5 to 5-1/2 inches), whereas males of
_muticus_ and some _T. spinifer emoryi_ are sexually mature at a
plastral length of 8.0 to 9.0 centimeters (length of carapace 11.2 to
12.6 cm. or 4-1/2 to 5 inches). The smaller adult males are probably
sexually mature in their fourth growing season. Breckenridge (_op.
cit._:7, Tab. II) commented on the abundance of females between five
and 12 inches in length, and males that ranged in length from five to
seven inches. The abundance of turtles in these size ranges is
probably due, in part, to a slowing of the rate of growth indicating
the approach of sexual maturity; the abundance of the smallest males
is especially in accord with the size at sexual maturity of males
(about five inches).

The largest acceptable record of size of _spinifer_ is 18 inches in
length of carapace (Breckenridge, 1957:232). Stockwell (1878:402),
however, wrote that females of _spinifer_ attain "an extreme length of
from twenty-four to twenty-eight, and, in rare instances, thirty
inches, with an average length of carapace of fifteen to eighteen,"
and True (1893:152) mentioned lengths of two feet or even more.
Turtles 17 to 18 inches long are doubtless rare and probably about 60
years old. A specimen of _ferox_ lived the longest time in
captivity--25 years (Pope, 1949:304). Individuals of _ferox_ probably
exceed the maximum recorded length of carapace of 18-1/2 inches
(Agassiz, 1857:401). The head of a _ferox_ having a width of 3-1/2
inches (Wright and Funkhouser, 1915:120) corresponds to a length of
carapace of approximately 22-1/2 inches (PL/HW == 4.9; CL/PL == 1.3).
De Sola and Abrams (1933:12) wrote that _ferox_ in the Okefinokee
Swamp, Georgia, attains a length of two feet. The largest female of
_muticus_ of which I have record is 21.5 centimeters in plastral
length (KU 2308), a measurement corresponding to a carapace about 13
inches long.

Mortality

Man, in one sense or another, is a great enemy of soft-shelled
turtles. Those caught by fishermen are destroyed because of the
erroneous belief that they are harmful to fish populations. Some are
drowned in hoop-nets or gill nets used by commercial fishermen. Many
softshells are used by man for food. Herald (1949:118-19) reported the
results of spraying an area with DDT and mentioned a 10-inch
individual of _ferox_ that was eating a dead bluegill, and which
"probably died as a result of ingesting contaminated food."

Predation on eggs probably accounts for most mortality. Hamilton
(1947:209) reported tracks of spotted skunks, raccoons and foxes seen
about destroyed nests, and Cahn (1937:183) incriminated skunks and
raccoons. Goldsmith (1945:449) reported a raccoon that unearthed seven
nests in one night. Little and Keller (1937:221) wrote of egg shells
found in the sand (probably not as a result of hatching), and Muller
(1921:182) reported egg shells around dug-up nests, suggesting such
predators as "ground moles," raccoons and crows. Chesser (_in_ Harper,
1926:416) said that in the Okefinokee Swamp the jackdaw (fish crow),
raccoon, bear and domestic dogs will eat the eggs. Wright and
Funkhouser (1915:122) recorded a young _ferox_ in the stomach of a
water moccasin (_Agkistrodon piscivorus_), and suggested that young
soft-shells probably are food of larger snakes. Kellogg (1929:26)
wrote that stomachs of two alligators each contained one soft-shelled
turtle. Newman (1906:136) found that young captives were eaten by
individuals of _Chrysemys_ and _Sternothaerus_, and I found that they
were eaten by _Kinosternon_. Mitsukuri (1905:261-62) stated that
first- and second-year individuals of _T. sinensis_ are eaten by the
adults.

Breckenridge (1960) wrote that a clutch of eggs probably failed to
develop because of an "... unusually cool season." Evermann and Clark
(1920:595) stated that "many young appear to perish during the first
winter." They (_op. cit._:594) found two eggs submerged in two feet of
water and it is supposed that they never hatched. Dundee (1950:139)
reported remains of soft-shelled turtles left on the mud of a dried
swamp.

Parasites

Muller (1921:182) found maggots in a few eggs of a clutch, but thought
that only the infertile and decomposing eggs were infested. I removed
a hard, spherical cyst from the hind leg of a preserved softshell
(TU). A captive hatchling (TU 17304) died as the result of a
continuously enlarging and deepening hole on the top of its head; I
could not discern a visible parasite with the naked eye. I found 25
leeches (_Placobdella parasitica_, largest about 13 mm.; identified by
Dr. Kenneth B. Armitage, Department of Zoology, University of Kansas)
in association with 11 _T. m. muticus_ (number per turtle not known)
that were collected from the Kansas River at Lawrence, Douglas County,
Kansas. Evermann and Clark (1920:596) reported a few nematodes in the
stomachs of some _spinifer_, and three nematodes are listed by Harwood
(1932:46, 60, 62, 66) in the same species. Hughes, Higginbotham and
Clary (1941) have listed the known reptilian hosts of parasitic
trematodes, and Hughes, Baker and Dawson (1941) have done the same for
tapeworms. The species of parasites and their trionychid hosts are
listed below.

TREMATODA
_Trionyx ferox_: _Neopolystoma orbiculare_ _Vasotrema amydae_
_Neopolystoma rugosa_ _Vasotrema attenuatum_
_Polystomoides coronatus_ _Vasotrema robustum_
_Teloporia aspidonectes_

_Trionyx muticus_: _Crepidostomum cooperi_ _Opisthorchis ovalis_

_Trionyx spinifer_: _Hapalorhynchus evaginatus_ _Vasotrema amydae_
_Opisthorchis ovalis_ _Vasotrema attenuatum_
_Polystomoides coronatus_ _Vasotrema longitestis_
_Teloporia aspidonectes_ _Vasotrema robustum_

CESTODA
_Trionyx ferox_: _Proteocephalus trionychinus_

_Trionyx spinifer_: _Proteocephalus testudo_

NEMATODA
_Trionyx spinifer_: _Camallanus trispinosus_ _Spiroxys amydae_
_Falcaustra chelydrae_

Economic Importance

Several authors have mentioned softshells as a food item much sought
after by man. The commercial value of these turtles has been
summarized by Clark and Southall (1920:15-16). Softshells are consumed
in quantity only in small towns near the place of capture. They are
found only occasionally in the markets of large cities because the
turtles are little known and the palatability of their flesh is
unappreciated. Also, they do not stand shipment so well as other
turtles, and they are "not so meaty as the snapper; so there is more
waste" (Clark and Southall, _loc. cit._). Little and Keller (1937:221)
reported living individuals for sale at the market in Ciudad Juarez,
Chihuahua; however my inquiry at markets in Juarez in the summer of
1959 disclosed no evidence of recent sale of soft-shelled turtles. In
the southeastern United States the demand is perhaps greater than in
other regions. I have noted softshells in the market at New Orleans,
and Oliver (1955:19) has mentioned the sale of "some 146,600 pounds"
in one recent year in Florida. Over most of their range, however,
there probably is no general demand for softshells and no special
efforts are made to capture them. Softshells have been raised
successfully on "turtle farms" in Japan (Mitsukuri, 1905). True
(1893:152) wrote that "The eggs also are considered very excellent."

Softshells generally are condemned by fishermen because of the
mistaken belief that they are detrimental to fish populations. Food of
softshells is principally crawfish and insects. Fish comprise a small
proportion of the diet (frequency 1.9% in Michigan, Lagler, 1943: Tab.
9). Most of the fishes eaten seem to be small minnows. Probably fish
would comprise a larger percentage of the diet if they could be
caught. I doubt that a softshell can pursue and capture a healthy fish
in natural waters. Recently dead fish are eaten and perhaps fish eggs,
and senile and decrepit fishes. There is no evidence that soft-shelled
turtles are active predators on any kind of fish. Of course in
congested areas such as ponds of fish hatcheries, it is desirable to
eliminate the turtles. The known food habits of soft-shelled turtles
suggest that they compete with game fishes for food, but there is no
information on the intensity of competition (Lagler, _op. cit._:305).

The combined statements of many authors in their general accounts of
food habits (for instance, Babcock, 1919:425) have tended to create
the erroneous belief that soft-shelled turtles harm waterfowl. To my
knowledge the only basis for this belief is the statement of Wright
and Funkhouser (1915:123) that according to the natives of the
Okefinokee Swamp, the larger turtles "devour also such waterfowl as
are unfortunate enough to be taken unaware by these reptiles." Perhaps
an occasional waterfowl is eaten, but the present information on kinds
of food eaten certainly does not warrant the destruction of
soft-shelled turtles. There may be some mortality in congested areas
such as game refuges where young birds crowd the surface of the water.

The kind of bait successfully used in trapping softshell turtles
suggests that they are of some value as scavengers.

EVOLUTIONARY HISTORY

Before attempting to reconstruct the history of soft-shelled turtles
in North America, it will be helpful to summarize the salient facts
concerning the distribution and relationships of the living forms, and
to comment on fossils.

Distribution

The geographic range of the family Trionychidae in North America is
principally in the eastern two-thirds of the continent and contributes
to the well-known floral and faunal resemblance of eastern North
America to that of eastern Asia (Schmidt, 1946:149) because _Trionyx
ferox_ (see Fig. 18) resembles the species of the genus in Asia more
closely than it does any North American species. The Recent
distribution in America does not include the Neotropical region,
whereas the geographical range in the Old World extends south of the
equator (Fig. 1; Dunn, 1931:109, fig. 2; Gadow, 1909:333, fig. 72;
Hay, 1908:35, fig. 16).

American softshells occur in all river systems in the United States
and the two adjacent river systems on the east coast of México that
drain into the Gulf of México. Softshells inhabit streams of the Great
Plains and occur westward to the foothills of the Rocky Mountains in
the western tributaries of the Mississippi River. Only _T. s.
spinifer_ occurs in the southern part of the Great Lakes-St. Lawrence
drainage. Softshells are absent from the Atlantic Coast drainage
except the Hudson River and those rivers at least south of (and
including) the Pee Dee River in South Carolina.

_T. s. emoryi_ is not known to be indigenous west of the Río Grande
drainage, and has probably been introduced across the Continental
Divide via the Gila River in western New Mexico into the Colorado
River drainage of Arizona (Miller, 1946:46); the species undoubtedly
occurs in México on the Sonoran side of the Colorado River opposite
Baja California (Bogert and Oliver, 1945:417).

In the summer of 1959, I trapped turtles and with a specimen in hand
inquired about softshells occurring in the inland drainages of
northern México. From two collecting stations on the Río Nazas in
Durango, only specimens of _Pseudemys_ and _Kinosternon_ were
obtained; local inhabitants had neither seen nor heard of softshells.
Flooded conditions in August of 1959 permitted trapping in only one of
the inland drainages of northwestern Chihuahua, the Río Santa María;
only specimens of _Kinosternon_ were obtained. Local residents near
that river as well as those living near the Río Casa Grandes and Río
del Carmen had not seen or heard of softshells. A person that I judge
to be a competent observer reported seeing a softshell in June of 1958
in the Río Alamos (Arroyo Cuchujáqui) near Alamos, Sonora, in the Río
del Fuerte drainage on the west coast of México. I was a member of a
field party from the University of Kansas that visited that locality
in late January of 1959; only specimens of _Pseudemys_ and
_Kinosternon_ were collected. Possibly isolated populations occur in
streams of the Pacific Coast drainage of northern México. If so, they
may have entered Pacific Coast drainages by stream capture across the
Continental Divide. Several species of fish that are characteristic of
the Río Grande traversed the Sierra Madre Occidental at some former
time (presumably via the Río Conchos and Río Papigochic) and occur in
the Yáqui River drainage (Meek, 1904:xxxviii, xlvii; Miller,
1959:214-15, 217). Because of the probability that the Río Nazas at
some former time flowed north into the Río Grande (Meek, _op.
cit._:xxxiv), it is notable that softshells are absent in the Río
Nazas drainage; the Big Bend turtle, _Pseudemys scripta gaigeae_,
occurs in both drainages.

Relationships

Characters of _Trionyx ferox_ suggesting a closer resemblance to some
Old World members of the family than to the other three American species
are: large size; marked difference between juvenal and adult patterns on
the carapace; the marginal ridge; and the longitudinal ridgelike
prominences on the carapace, especially in juveniles. Other characters
of _ferox_ suggesting a corresponding, but less marked resemblance to
Old World species of _Trionyx_ are: the large size of the eighth pair of
pleurals; the absence of callosities on the epiplastron and preplastra;
frequent fusion of the hyoplastra and hypoplastra (more than in
_spinifer_ or _muticus_); and tolerance of marine waters (more than
_muticus_ or _spinifer_). Some fossils also suggest alliance with
_ferox_ and some Old World members of the genus in their large size,
large eighth pair of pleurals, and occurrence in marine deposits;
several Old World species have been reported at sea (_Pelochelys_, _T.
triunguis_, _T. sinensis_). _T. ferox_ is monotypic and has the most
southeasterly displaced, geographic range.

Because _ferox_ resembles softshells from the Old World more closely
than it does any American species, _ferox_ is assumed to be more closely
related to Old World softshells than to any American species, and,
because of resemblance to some fossils, _ferox_ is assumed to resemble
most closely the primitive, ancestral stock of softshells that occupied
North America. _T. spinifer_, _T. muticus_ and _T. ater_, which resemble
each other more closely than any of them resembles _T. ferox_ or any Old
World species, are considered autochthonous in North America. _T.
spinifer_ and _T. muticus_ are distinct, sympatric species. Burt
(1935:321) suggested that the two species "may be variants of the same
species." _T. ater_ is weakly differentiated from _T. spinifer emoryi_.
The species, _ferox_, _spinifer_ and _muticus_ are well-differentiated
and were considered by Agassiz (1857), Gray (1869) and Baur (1893) as
belonging to three different genera.

In the widely distributed _T. spinifer_, the subspecies _spinifer_,
_hartwegi_ and _asper_ closely resemble one another; _asper_ seems most
distinct, whereas _spinifer_ and _hartwegi_ are terminal populations of
an east-west cline in one character. The subspecies _pallidus_,
_guadalupensis_ and _emoryi_ resemble one another more closely than any
resembles any of the subspecies mentioned immediately above; _T. s.
pallidus_, however, is annectent. _T. s. pallidus_ and _guadalupensis_
represent terminal populations of clines in several characters, some of
which occur in _emoryi_, but that subspecies is more distinct from
_pallidus_ and _guadalupensis_ than those subspecies are from each
other. _T. s. emoryi_ is the most variable subspecies. _T. ater_, known
only from a restricted area in central Coahuila, is most closely related
to _T. s. emoryi_, and possesses some characters judged to represent the
attenuation of the geographic cline in _pallidus_, _guadalupensis_ and
_emoryi_ mentioned above. Some characters of _ater_ show alliance to the
species _muticus_. Of _T. muticus_, whose geographic range is removed
from that of _ater_, there are two subspecies. Four subspecies of
_spinifer_ (_spinifer_, _hartwegi_, _pallidus_ and _asper_) intergrade
in the Mississippi River drainage of Louisiana; few specimens, however,
are typical of _asper_. The subspecies of _muticus_ do not show definite
evidence of intergradation. To facilitate quick reference, the
occurrence of some characters that are shared by, or are approximated
in, two or more forms are listed in Table 10. In addition to external
characters, some ratios emphasize the clinal relationship between _T. s.
pallidus_, _guadalupensis_, and _emoryi_ mentioned above. Of especial
interest is the frequent resemblance of those subspecies and _T. ater_
to _T. ferox_ (dorsal pattern on limbs of adults, reduction in anterior
tuberculation, wide head, narrow carapace, and short snout), and the
less marked resemblance of _T. muticus_ to _T. ferox_; not shown in
Table 10 is the resemblance of _ferox_ to _T. muticus calvatus_ in
having thick, black-bordered postocular stripes. Some populations of _T.
s. emoryi_ resemble _T. muticus_ in the corresponding size at sexual
maturity and in having well-developed plastral callosities. It is
notable that the occurrence of _ater_, and to a lesser extent that of
_T. s. emoryi_, which resembles _ferox_ (and _muticus_), is in the
southwestern United States and northern México.

TABLE 10. Frequency of Selected Characters Among Species and
Subspecies of Trionyx in North America. Characters of muticus
Refer to the Typical Subspecies; Horizontal Dashes Connecting
X's Indicate that Computations for Those Subspecies Were
Combined; Vertical Dashes Indicate that the Subspecies Is
Intermediate Between the Adjacent Subspecies.

Column headings:

A: _ferox_
B: _spinifer_
C: _hartwegi_
D: _asper_
E: _pallidus_
F: _guadalupensis_
G: _emoryi_
H: _ater_
I: _muticus_

=====================================+===================================
| Species and subspecies
Characters +---+---+---+---+---+---+---+---+---
| A | B | C | D | E | F | G | H | I
-------------------------------------+---+---+---+---+---+---+---+---+---
Juvenal pattern: | | | | | | | | |
black spots, ocelli | | X | X | X | | | | |
| | | | | | | | |
white dots | | | | | X | X | X | X |
-------------------------------------+---+---+---+---+---+---+---+---+---
Pattern on snout: | | | | | | | | |
acute angle (reduced in _muticus_) | X | X | X | X | X | | | | X
| | | | | ¦ | | | |
triangular | | | | | X | X | X | X |
-------------------------------------+---+---+---+---+---+---+---+---+---
Pattern on side of head: | | | | | | | | |
contrasting marks | X | X | X | X | X | X | | |
| | | | | | ¦ | | |
non-contrasting marks (distinct | | | | | | ¦ | | |
stripe in _muticus_) | | | | | | X | X | X | X
-------------------------------------+---+---+---+---+---+---+---+---+---
Pattern on limbs of adults: | | | | | | | | |
contrasting | | X | X | X | X | X | | |
| | | | | | ¦ | | |
reduced or absent | X | | | | | X | X | X | X
-------------------------------------+---+---+---+---+---+---+---+---+---
Tuberculation (anterior edge of | | | | | | | | |
carapace): | | | | | | | | |
conical, equilateral | | X | X | X | X | | | |
| | | | | | | | |
reduced or absent | X | | | | | X | X | X | X
-------------------------------------+---+---+---+---+---+---+---+---+---
Head (PL/HW, fig. 3): | | | | | | | | |
wide | X | | | X | | X | X | X |
| | | | | | | | |
narrow | | X | X | | X | | | | X
-------------------------------------+---+---+---+---+---+---+---+---+---
Carapace (CL/CW, fig. 4): | | | | | | | | |
wide | | X | X | X | X | X | | | X
| | | | | | ¦ | | |
narrow | X | | | | | X | X | X |
-------------------------------------+---+---+---+---+---+---+---+---+---
Level of Carapace Width (CL/PCW, | | | | | | | | |
fig. 5): | | | | | | | | |
middle of carapace | X | X | X | X | | | | | X
| | | | | | | | |
farther posteriorly | | | | | X | X | X | X |
-------------------------------------+---+---+---+---+---+---+---+---+---
Snout (HW/SL, fig. 6): | | | | | | | | |
long | | X---X | X | X---X | | | X
| | | | | ¦ ¦ | | |
short | X | | | | X---X | X | X |
-------------------------------------+---+---+---+---+---+---+---+---+---

Fossils

The known occurrence of fossil trionychids throughout the world
indicates a former distribution more widespread than the family has
today; the principal difference in the former and present distributions
is the lack of living softshells in Europe.

I have not studied in detail the many fossil remains but such
examination as I have made of them suggests that many of the characters
used as a basis for distinguishing fossil forms in North America are
subject to individual variation or are of no diagnostic value in the
living species (Hummel, 1929:769). Knowledge of the variation in the
living species of the Old World would aid in adequately appraising the
North American fossils. Some osteological characters of the three living
American species (excluding _ater_) together with data on variation
within a given species are mentioned below. Some differences in skulls
of the three species already were mentioned in the section "Osteological
Characters." Because most fossil remains are those of the carapace and
plastron, attention is here given to those structures.

_Widened alveolar surfaces of jaws._--An ontogenetic variation
affecting large skulls of _T. ferox_ and some individuals of _T.
spinifer asper_; presumably confined to females. Of especial interest
is its presence in some populations of _asper_ that are not otherwise
distinguishable (external characters) from the rest of the individuals
comprising that subspecies.

_Sculpturing._--No differences in pattern (generally of anastomosing
ridges) on carapace or plastron; fineness or coarseness seemingly
correlated with size; frequency and kind (knoblike or ridgelike) of
bony prominences on carapace variable; bony prominences confined to
species _spinifer_ and _ferox_, occurring principally on large
females.

_Fontanelles of carapace._--Closure more or less correlated with
increasing size, although much variation noted between individuals of
same size; small individuals have fontanelles confluent (medially),
thus separating nuchal from contact with first neural and first pair
of pleurals.

_Number and arrangement of neurals and pleurals._--Neurals number six
to nine, usually seven or eight; pleurals number seven or eight pairs,
and may or may not be in contact with each other posteriorly; eighth
pair of pleurals when present reduced, never contacting seventh
neural; arrangement posteriorly variable (see Fig. 16 and Tab. 5).

_Plastral callosities._--Increase in size with advancing age causing
corresponding reduction in size of plastral vacuity; relatively best
developed in _muticus_ (all elements touching medially on KU 41380
leaving no plastral vacuity); probably no callosities on preplastra or
epiplastron of _ferox_; callosity on epiplastron of _spinifer_ not
covering entire surface (as it may in _muticus_).

_Epiplastron._--Obtusely-angled (greater than 90 degrees) in
_muticus_; acutely-angled (90 degrees or less) in _ferox_ and
_spinifer_.

_Hyo-hypoplastral suture._--Usually present, but occasionally absent,
in all species.

The fossil turtles of North America have been treated monographically by
Hay (1908), who apportioned fossil trionychid remains into eight genera
(three living) of two families. Recently, Romer (1956:514) relegated all
trionychid fossils to the genus _Trionyx_. Characters, as gleaned from
Hay's synopsis (_op. cit._:465-548, Pls. 85-113), that seem especially
worthy of taxonomic consideration are: (1) The presence of a preneural,
which is not known to occur in the living American species (seemingly
the preneural is fused with the first neural and represents the elongate
first neural in living species); (2) The large eighth pair of pleurals,
especially when they contact the seventh neural; (3) The thickness of
the costal plates, a condition probably correlated with the size of some
fossils, which are larger than any living species (for example, Hay,
_op. cit._:518, mentioned the greatest dimension of a nuchal bone as
approximately 300 mm.).

The approximate extent of the known horizontal distribution of fossils
is indicated in Figure 24. A comparison of known localities of fossils
and the distribution of living softshells (introduced population of _T.
s. emoryi_ in Colorado River drainage omitted) shows that the
distribution was more widespread in former times. Localities of fossils
are centered on the Atlantic Coast from New Jersey to North Carolina and
in the Rocky Mountain-Great Plains region from Alberta and Saskatchewan
to northwestern New Mexico; the oldest fossils, which occur in each
region, are found in Upper Cretaceous deposits. Many fossils occur in
marine and brackish water deposits. Most localities depicted on the map
are mentioned by Hay (1908:36-37, 465-548). Other localities included on
the map are in southern Alberta (Russell, 1929:164; 1930:27; Sternberg,
1926:104), southern Saskatchewan (Russell, 1934:109), northern South
Dakota (Hay, 1910:324), central Utah (Gilmore, 1946), western Colorado
(Schmidt, 1945), southwestern Kansas (Galbreath, 1948:284), southeastern
Texas (Hay _in_ Stejneger, 1944:65), southern California (Brattstrom,
1958:5), and northeastern Coahuila, México (Mullerried, 1943:623). Hay's
record of the living _Platypeltis_ (= _Trionyx_) _ferox_ and other
remains from the Peace Creek formation in Hillsborough County, Florida
(_op. cit._:548), presumably is the same record mentioned by Pope
(1949:305).

[Illustration: FIG. 24. Geographic distribution of Recent
soft-shelled turtles (bordered by heavy black line) and fossil
trionychids (black circles) in North America. The introduced
population of _T. s. emoryi_ in the southwestern United States
is not shown.]

Ameghino (_in_ Hay, _op. cit._:35) recorded specimens of a trionychid
from the Cretaceous of Patagonia, a record that, at present, cannot be
accepted (Simpson, 1943:423). Mullerried (_loc. cit._) also mentioned
some trionychid remains that were housed in Tuxtla Gutierrez, Chiapas,
México, (material now lost), but their geographical provenance was
unknown. The former extent of range southward is not known; it is
improbable that trionychids occurred in South America (Simpson,
1943:423).

Phylogeny

The occurrence of _T. ferox_ in Florida and the suggestion of
_ferox_-like characters in turtles from southwestern Texas and northern
Mexico presents a distributional pattern that resembles the disjunct
ranges of many other pairs of closely related taxa. The clear-water
ponds in central Coahuila, which are inhabited by _ater_, correspond to
aquatic habitats supporting _ferox_ in Florida. The splitting of the
geographic range into eastern and western parts possibly resulted from a
southward shift of colder climates in glacial stages of the Pleistocene,
or from the development of an intervening arid region in the late
Miocene and Pliocene (see discussions in Martin and Harrell, 1957, and
Blair, 1959). An initial separation of range by an arid environment in
the Pliocene may have been terminated by the colder climates in the
Pleistocene.

The degree of morphological difference between _ferox_ and the forms in
southwestern Texas and northern México, suggests that the time of
separation antedated the Pleistocene.

Trionychid turtles may have traversed the Bering land bridge between
Asia and North America in late Mesozoic times for they occur as fossils
on the Atlantic Coast and in the Rocky Mountain-Great Plains region in
Upper Cretaceous deposits. Shallow, inland seas may have afforded no
barrier to the dispersal of softshells which presumably were tolerant of
saline waters. The orogeny and volcanic action with subsequent erosion
and sedimentation of the Rocky Mountain system, which was later
accompanied by drier climates, tended to obliterate suitable habitats in
the western United States; softshells persisted at least until the Upper
Eocene on the west coast (Brattstrom, 1958:5). The factors responsible
for the disappearance of softshells on the Atlantic Coast probably were
related to the glacial advances in the Pleistocene; the most recent
fossils known occur in Miocene deposits.

The relationships of the living species and subspecies were probably
correlated with geologic change in aquatic environments and drainage
patterns. These changes probably included stream capture, flooding,
drought, uplifting and planation. A hypothetical, evolutionary history
is presented in the phylogenetic diagram where letter symbols represent
species and subspecies, and grouped symbols (referred to in subsequent
paragraphs) represent ancestral stocks.

Pliocene Pleistocene Recent
==========================================================================

--------------------------------------------------------------------------

An arid environment in the central and southern United States and
northern Mexico may have increased in area especially southward from
Miocene times into the Pliocene (Dorf, 1959:189, 191). The combination
of physiographic changes and aridity, which modified the mesic,
essentially continuous, aquatic habitats, may have isolated and aided in
the differentiation of the _ferox_, _muticus_ and _spinifer_ stocks.
Encroachment of the Eocene seas, the maximal extent of which
corresponded to the Gulf Coastal Plain and included a northerly
extension as far as Cairo in southern Illinois (Mississippi embayment),
possibly was an initial barrier isolating the _ferox_ stock of the east.

In the late Miocene or early Pliocene, the MSA (_muticus-spinifer-ater_)
stock presumably occupied a large region of the central United States,
which extended southward into northern México and along the Gulf Coast
at least as far as Alabama. Farther eastward, the _ferox_ stock was
isolated in more mesic, probably swampy, marshy habitats.

Later, in the southwestern part of the range of the MSA stock (southern
Texas and northern México), the SA and _muticus_ stocks were separated.
The _muticus_ stock occurred to the northeastward, and presumably no
farther south than the area included within the present drainage basin
of the Colorado River. Southward, the SA stock was isolated into several
populations that are today represented by _ater_ and _T. s. emoryi_, the
most variable subspecies; the distribution of the most distinctive
population of _emoryi_ indicates a former isolated inland drainage. The
multiple fragmentation of the SA stock presumably terminated by the end
of the Pliocene. The progenitors of _T. ater_ probably closely resembled
_ferox_. _Trionyx ater_ and _T. ferox_ resemble each other
morphologically and in habitat. Therefore, the progenitors of _ater_ are
considered to have undergone comparatively little differentiation.

The _spinifer_ stock, occurring principally in the area included within
the present drainage basin of the Río Grande, extended its geographic
range eastward and became sympatric with _muticus_ and _ferox_. An
expansion of range necessarily demands more mesic conditions; these were
perhaps afforded by the pluvials (wet, rainy ages) that were coincident
with the glacial periods in the Pleistocene (Antevs, 1948:168). The
pluvials permitted the isolated populations of the _spinifer_ stock to
unite, and permitted that stock to extend its range eastward. The
concurrent continental glaciation permitted the _spinifer_ stock to
extend its range eastward only in a belt approximately 300 miles wide
along the Gulf Coast, and also displaced the ranges of _ferox_ and
_muticus_ to southern latitudes. Perhaps _ferox_ was less tolerant of
decreased temperatures or changes in habitat than was the _spinifer_
stock but, for some unknown reason, _ferox_ did not extend its range
westward. Because _T. ater_ closely resembles _T. s. emoryi_, continued
isolation of _ater_ since the beginning of the Pleistocene seems
unlikely and _ater_ may have been reunited in subsequent pluvial periods
with the _spinifer_ (_emoryi_) stock. A climatic fluctuation between
relatively wet and dry periods is corroborated by studies of soil
profiles in Trans-Pecos Texas (Bryan and Albritton, 1943).

The separation of the range of _spinifer_ in the general region of
western Louisiana, resulting in the differentiation of the _spinifer_
group of subspecies to the east and the _emoryi_ group of subspecies to
the west, and the differentiation of _T. s. asper_ and _T. m. calvatus_,
both having corresponding western limits of distribution (Mississippi
River drainage), are associated with the activities of the Mississippi
River and its flood-plain. The combined effects of the pluvials and
interpluvials seem responsible for changes in the lower Mississippi
Valley. Great volumes of summer melt-water in the glacial stages greatly
increased the breadth of the channel of the lower Mississippi River
(corresponding to the northern extent of the Mississippi embayment;
Hobbs, 1950), and this, coupled with the encroachment of Pleistocene
seas (especially in the Mississippi embayment) in the interglacial
periods, perhaps separated populations eastward represented today by _T.
m. calvatus_ and _T. s. asper_. The _spinifer-hartwegi_ stock probably
developed in southern Louisiana in association with the meandering of
the Mississippi River and its tributaries, and its broad alluvial plain.
The biota of that plain differed from that adjacent to the east or west
(see discussion in Viosca, 1944) and constituted a barrier, of a sort,
to free communication between the east and west. Westward the _emoryi_
group of subspecies differentiated, its eastern limit probably being the
Red River, which followed its own course to the Gulf along the lowlands
on the west side of the Mississippi Valley and did not empty directly
into the Mississippi until Recent times (Holland, 1944:20). There was
not an equally-marked, corresponding separation of the range of
_muticus_. However, the juvenal pattern of the subspecies _muticus_ that
inhabits the Gulf Coast streams is slightly different (having less short
lines) from that of _muticus_ elsewhere.

The Río Grande (inhabited by _emoryi_) presumably had its own exit to
the Gulf whereas rivers westward to (and including) the Red River
(inhabited by _pallidus-guadalupensis_ cline) probably were joined near
their mouths forming a large drainage system. Hubbs (1957:93) pointed
out that the Río Grande-Nueces divide also limits a large number of
species of fish. The differentiation of _pallidus_ and _guadalupensis_
is possibly due to a difference in the salt content of waters that drain
the Edward's Plateau (see page 547), or to isolation of those subspecies
in separate drainage systems that had their own exits to the Gulf.

In the lower Mississippi drainage, the _spinifer-hartwegi_ stock
extended its range northward following the retreat of the last glacial
stage, and differentiated into those two subspecies in the upper
Mississippi drainage and Great Lakes-St. Lawrence drainage system.

I have seen one specimen (UMMZ 59198) from the eastern part of the
Tennessee drainage (inhabited by _T. s. spinifer_) that resembles _T. s.
asper_ (occupying the Gulf Coast drainages of the southeast). This
resemblance tends to support the thesis of a former confluence of the
Coosa (Alabama River system) and Tennessee drainages as believed by some
malacologists to explain resemblances in molluscan fauna and as
corroborated by physiographical evidence (see discussion in van der
Schalie, 1945).

The Importance of the Study of Turtle Populations in Relation to the
History of River Systems

In the Río Grande drainage the geographic distribution of the population
of _emoryi_ having orange color in males is approximately the same as
that of _Pseudemys scripta gaigeae_; the corresponding distributions
suggest that a part of the Río Grande drainage consisting of the Río
Conchos in Chihuahua and the Big Bend region of Texas was isolated in
former times. Accordingly, the known aquatic chelonian fauna in the
basin of Cuatro Ciénegas in central Coahuila, México, is endemic (except
_T. s. emoryi_). And the coincidence of the geographic ranges of _T.
muticus calvatus_ and _Graptemys pulchra_ in the southeast suggest a
former association of the included (Pearl to Escambia) river systems.
The occurrence of _T. s. pallidus_ in the Red River drainage indicates
that the Red River was formerly associated with the Gulf Coast streams
of eastern Texas and western Louisiana (inhabited by _pallidus_) and not
with the Mississippi River drainage. The lower Mississippi River valley
forms a prominent barrier to the eastern and western dispersal of many
kinds of species and subspecies of turtles. _T. m. calvatus_ and _T. s.
asper_, which occur in rivers of the Gulf Coast drainage east of the
Mississippi, are well-differentiated subspecies showing little or no
evidence of intergradation with their relatives in the Mississippi
River. The large faunal break provided by the Mississippi River would
seem to indicate greater age for that river than for other rivers of the
Gulf Coast drainage.

A comparison of the distributions of _Trionyx_ and _Graptemys_ in Texas
suggests a faunal break between the drainage systems of the Brazos and
Colorado rivers. _Graptemys versa_ occurs in the Colorado and
Guadalupe-San Antonio drainages. To my knowledge _versa_ hitherto has
not been recorded from the latter drainage system. I have seen one
specimen of _Graptemys_ (custody of Gerald Raun, University of Texas)
from the Guadalupe River drainage, which I judge to be representative of
_versa_, and Olson (1959:48) has reported _Graptemys_ (probably _versa_)
in the San Antonio River. The distribution of _G. versa_ parallels in a
general way, the distribution of _T. s. guadalupensis_. _G. kohni_ and
_T. s. pallidus_ occur in the Brazos River and eastward. Also, it is
notable that the population of _T. m. muticus_ occurring in the Colorado
River drainage differs slightly (more black pigmentation) from the same
subspecies in the adjacent Brazos River system.

There is much difference in the patterns of distribution and degree of
differentiation of different genera of aquatic turtles in the eastern
United States. Tinkle (1958:41-43, Figs. 49-55) concluded that a general
resemblance in the patterns of distribution of the different genera of
turtles was evidence that the rates of evolution were essentially the
same, assuming that each genus had had a similar time interval for
differentiation (_op. cit._:42). If this is true, corresponding patterns
of distribution might indicate the same relative age of the population
of turtles concerned. Generally, the genera of turtles that on
morphological grounds are considered the oldest and most primitive
(_Macroclemys_, _Chelydra_) show less differentiation into species and
subspecies than those considered younger and more recently evolved
(_Graptemys_, _Pseudemys_). In the genus _Graptemys_, much
differentiation occurs in the geologically, recently formed, Gulf Coast
drainage systems of the southeastern United States. It would seem then,
that faster rates of differentiation denote more recent genera, whereas
older genera are endowed with a "genetic senility" and are less subject
to change.

Evidence of the relative age of two genera of turtles, as suggested by
their degree of differentiation into minor taxa, and the degree of
difference between populations of two genera that inhabit adjacent
drainage systems, may indicate the relative ages of particular river
systems. For example, the slight resemblance of _G. versa_ to _kohni_
and the close resemblance of _T. s. guadalupensis_ to _pallidus_ in
Texas may reflect the age of the genus _Trionyx_ and the youth of the
genus _Graptemys_. Remembering that the genus _Graptemys_ is relatively
recently evolved and assuming _G. versa_ to be the most primitive and
ancestral species of the genus (at least it is monotypic, the most
aberrant species, and unlike any other species of the genus), it seems
logical to suppose that the physiographic changes responsible for the
Colorado-Brazos divide and the isolation of _versa_ occurred early in
the evolutionary history of the genus _Graptemys_. The degree of
differentiation of _Trionyx_ suggests that that genus is, comparatively,
much older, and that the same physiographic changes responsible for the
Colorado-Brazos divide and differentiation of the subspecies _pallidus_
and _guadalupensis_ occurred late in the evolutionary history of the
genus _Trionyx_.

In general, patterns of distribution of turtle populations support
physiographic evidence concerning changes in stream confluence and
relative age of river systems.

SUMMARY

In North America, soft-shelled turtles (genus _Trionyx_) occur in
northern México, the eastern two-thirds of the United States, and
extreme southeastern Canada. The genus fits the well-known Sino-American
distributional pattern. In North America there are four species. Three
(_ferox_, _spinifer_ and _muticus_) are well-differentiated and one
(_ater_) is not well-differentiated from _spinifer_. Characters of
taxonomic worth are provided by the following: size; proportions of
snout, head and shell; pattern on carapace, snout, side of head, and
limbs; tuberculation; sizes of parts of skull; number of parts of
carapaces; and, shape and number of some parts of plastra. Many features
show geographical gradients or clines. _T. ferox_ is the largest species
and _muticus_ is the smallest. Females of all species are larger than
males. With increasing size of individual, the juvenal pattern is
replaced by a mottled and blotched pattern in females of all species;
adult males of _spinifer_ retain a conspicuous juvenal pattern, whereas
the juvenal pattern is sometimes obscured or lost on those of _ferox_
and _muticus_. The elongation of the preanal region in all males, and
the acquisition of a "sandpapery" carapace in males of _spinifer_ occur
at sexual maturity. There is a marked secondary sexual difference in
coloration in a population of _T. s. emoryi_ (side of head bright orange
in males and yellow in females). The sex of many hatchlings of _T. s.
asper_ can be distinguished by the pattern on the carapace. Slight
ontogenetic variation occurs in some proportional measurements. Large
skulls of _ferox_ and some _asper_ (those in Atlantic Coast drainages)
have expanded crushing surfaces on the jaws. Considering osteological
characters, _muticus_ is most distinct; there is less difference between
_ferox_ and _spinifer_ than between those species and _muticus_.

_T. ferox_ is monotypic, confined to the southeastern United States, and
resembles Old World softshells more than it does any American species.
The northern part of the geographic range of _ferox_ overlaps that of
_T. s. asper_; there, the two species are ecologically isolated. _T.
spinifer_ is polytypic, has the largest geographic range, and is
composed of six subspecies, of which two are described as new
(_pallidus_ and _guadalupensis_). The subspecies are divisible into two
groups. One, the _spinifer_ group (_spinifer_, _hartwegi_ and _asper_)
is recognized by a juvenal pattern having black spots or ocelli; _asper_
is the most distinctive and shows little evidence of intergradation in
the lower Mississippi River drainage with the _spinifer-hartwegi_
complex, which, northward, is differentiated into two subspecies in
which there is an east-west cline in size of the ocelli on the carapace.
The _emoryi_ group (_pallidus_, _guadalupensis_, _emoryi_) is recognized
by a pattern of white spots; _emoryi_ is most distinctive. Each of
several characters behaves as a cline if traced from east to west
through the three subspecies. _T. s. pallidus_ intergrades with the
_spinifer-hartwegi_ complex in the lower Mississippi River drainage. _T.
s. emoryi_ is the most variable subspecies; in its most notable
population the males have orange coloration. _T. s. emoryi_ has been
introduced into the Colorado River drainage of Arizona. _T. ater_ most
closely resembles _T. s. emoryi_, but shows alliance with _T. muticus_
and _T. ferox_. _T. ater_ is confined to ponds of crystal-clear water in
central Coahuila, México. _T. muticus_ is completely sympatric with
_spinifer_, and is composed of two subspecies (_muticus_ and
_calvatus_). _T. m. calvatus_ shows no evidence of intergradation in the
lower Mississippi River drainage with _T. m. muticus_, corresponding
somewhat to the relationship of _T. s. asper_ with the intergradient
population of _T. spinifer_ in the Mississippi River.

Softshells have pharyngeal respiration and probably are incapacitated by
rotenone. _T. ferox_ and the subspecies of _spinifer_ occur in a wide
variety of fresh-water habitats; _muticus_ is more nearly restricted to
running water (especially in the northern parts of its range) than
_spinifer_, and may be less vagile than _spinifer_. _T. ferox_ is more
tolerant of marine and brackish waters than are _muticus_ or _spinifer_.
Small size and pallid coloration seem correlated with arid environments.
The largest species (_ferox_) and the smallest population of _spinifer_
(resembling _muticus_) both occur in the southernmost part of the range
of the genus. Diurnal habits include basking on shores or débris in
water, floating at the surface, procuring food, and burrowing in shallow
and deep water (no observations for _spinifer_ and _muticus_ in deep
water). Softshells are principally carnivorous; the food consists mostly
of crawfish and insects; there is evidence of cannibalism involving
predation on first- and second-year-old turtles. The capture of food is
triggered primarily by movement of prey; sight seems to be more
important than smell to _Trionyx_ in capturing food. There is no
indication of a food preference between species; enlarged crushing
surfaces of jaws in some _ferox_ and _asper_ may be an adaptation for
feeding on mollusks. Schools of fish are reported to follow softshells,
and presumably acquire food that is dislodged by the grubbing and
scurrying of the turtles on the bottom. Softshells are wary. They are
good swimmers, and travel rapidly on land. The depressed body is an
adaptation for burrowing and concealment. Permanent growths of algae do
not occur on the dorsal surface of softshells. There is evidence of some
nocturnal activity, and a general parallel in habits between trionychids
and chelydrids. Softshells sometimes move overland; they move little in
aquatic habitats. The normal annual period of activity of _spinifer_ in
latitudes 40° to 43° is approximately five months from April into
September, depending on the weather; they hibernate under a shallow
covering of mud in deep water. The southernmost populations may be
active throughout the year.

Males of _spinifer_ are sexually mature when the plastron is 9.0 to 10.0
centimeters in length (some when 8.0 long), whereas those of _muticus_
are sexually mature at 8.0 to 9.0 centimeters. In the mentioned size
range, the smaller adult males are probably in their fourth growing
season, and the larger males in their fifth. Most females of _spinifer_
are sexually mature at a plastral length of 18.0 to 20.0 centimeters and
are probably in their ninth year; the smaller individuals probably are
in their eighth. Females of _muticus_ are sexually mature when the
plastron is 14.0 to 16.0 centimeters long. Most of these are seven years
old but some are only six years old. Some large females contain immature
ovaries. The near-maximum length of carapace of _spinifer_ is 18 inches,
and such turtles are perhaps 60 years old; _ferox_ perhaps attains a
length of two feet.

_T. ferox_ deposits eggs from late March to mid-July, whereas northern
populations of _spinifer_ and _muticus_ usually deposit theirs from
mid-June to mid-July. Sandy sites are preferred for nests, although
movement to other sites occurs if the preferred sandy sites are
submerged or otherwise rendered unusable. _T. muticus_ limits its nest
sites to the open areas of sand bars and does not lay inland where it
must traverse vegetated areas, as does _spinifer_. Nests of _ferox_ and
_spinifer_ seem to differ from those of _muticus_ in being flask-shaped.

The seasonal reproductive potential is perhaps less in northern
populations (averaging 20 eggs per clutch and only one clutch per
season) than in southern populations (averaging about 10 eggs per
clutch, but three clutches per season). Larger females deposit more eggs
than smaller females. Eggs laid in northern latitudes are slightly
smaller than those laid farther south. In any latitude the incubation
period probably is at least 60 days. Hatchlings presumably leave nests
at dusk, nighttime or dawn, and may winter over in eggs or nests.

Man is a great enemy of softshells. Predation on eggs probably accounts
for most mortality. Physical conditions of the environment (overcrowding
of nest sites, inadequate hibernation sites) and probably some kinds of
parasitism contribute to mortality. Softshells are eaten locally and
sometimes appear in the market of large cities, but over most of their
range, there probably is no general demand and no special efforts are
made to capture them. Fish, mostly minnows, comprise a small proportion
of the diet. There is no evidence that softshells are active predators
on any kind of fish, but their known food habits suggest that they
compete with game fishes for food. Softshells are scavengers.

Fossil material was not studied in detail. The fossil softshells
indicate a more widespread, former distribution. Some osteological
characters and their variation in the living species are mentioned as an
aid to future workers concerned with an assay of fossil remains. Fossils
occur in marine, brackish and fresh-water deposits, and many are much
larger than the living species; the oldest American fossils are of Upper
Cretaceous age.

The interrelationships of the living species and subspecies suggest that
the species _spinifer_, _ater_, and _muticus_ are derivatives of a
_ferox_-like ancestor, and that they differentiated in North America;
most differentiation occurs in southwestern Texas and northern México
where characters of some populations indicate alliance with _ferox_. It
is hypothesized that aridity in the late Tertiary effected specific
differentiation by the modification and isolation of aquatic habitats.
Pluvial periods in the Pleistocene provided for confluence of aquatic
habitats and expansion of geographic ranges, and coupled with
physiographic changes, conceivably caused or enhanced some of the
subspecific variation.

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1937. Amphibians and reptiles of the Jornada Experimental Range,
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1957. The Pleistocene history of temperate biotas in Mexico and
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_Transmitted June 8, 1961._

[Illustration: PLATE 31

_Trionyx ferox_, juveniles. _Top_--UMMZ 76755 (× 1) dorsal and
ventral views; Lake Griffin, Lake County, Florida. _Bottom_--TU
13960 (× 3/4), dorsal and ventral views; Hillsborough River,
_ca._ 20 mi. NE Tampa, Hillsborough County, Florida.]

[Illustration: PLATE 32

_Top_--_Trionyx ferox_, female, UMMZ 90010 (× 2/9); east edge
Okefinokee Swamp, Charlton County, Georgia. _Bottom_--Left,
_Trionyx ferox_, adult male, UMMZ 102276 (× 1/5), 14 mi. SE Punta
Gorda, Lee County, Florida; right, _Trionyx sinensis_, female, KU
39417 (× 3/10), 5 mi. ESE Seoul, Korea. All dorsal views; note
resemblance of two species in having longitudinal ridging and
marginal ridge of carapace.]

[Illustration: PLATE 33

_Trionyx spinifer spinifer_, juveniles, dorsal views.
_Top_--UMMZ 74518 (× 1-2/5); Portage Lake, Washtenaw County,
Michigan.
_Bottom_--TU 16132 (× 1-1/5); Sevierville, Sevier County,
Tennessee.]

[Illustration: PLATE 34

_Trionyx spinifer spinifer_, dorsal views.
_Top_--Adult male, UMMZ 54401 (× 3/7), Portage Lake,
Livingston County, Michigan.
_Bottom_--Female, UMMZ 81699 (× 2/7), Ottawa County, Michigan.]

[Illustration: PLATE 35

_Trionyx spinifer hartwegi_, dorsal views.
_Top_--Juveniles; left, KU 40210 (× 9/10), 12-1/2 mi.
S, 1-1/4 mi. W Meade, Meade County, Kansas; right, KU 16531
(× 1), Smoky Hill River, 3 mi. SW Elkader, Logan County, Kansas.
_Bottom_--Adult Males; left, KU 18385 (× 2/5), Arrington,
Comanche County, Kansas; right, KU 3758 (× 3/10),
Little Salt Marsh, Stafford County, Kansas.]

[Illustration: PLATE 36

_Trionyx spinifer hartwegi._
_Top_--Juveniles; left, TU 13885, dorsal view (× 3/4),
Little Vian Creek, 1 mi. E Vian, Sequoyah County, Oklahoma;
right, KU 3732, ventral view (× 5/7), Independence,
Montgomery County, Kansas.
_Bottom_--Adult female, TTC 719, dorsal view (× 2/7), 10 mi. S,
2 mi. W Gruver, Hansford County, Texas.]

[Illustration: PLATE 37

_Trionyx spinifer asper_, juveniles, dorsal views.
_Top_--Left, male, KU 50839 (× 9/10), Flint River, 1-1/2 mi. S
Bainbridge, Decatur County, Georgia; right, female, TU 15661
(× 9/10), Blackwater River, 4.3 mi. NW Baker, Okaloosa County,
Florida.
_Bottom_--Left, male, TU 13623 (× 7/9), Yellow River, 3.1 mi. W
Hammond, Tangipahoa Parish, Louisiana; right, female, TU 14362
(× 4/5), Hobolochito Creek, 1 mi. N Picayune, Pearl River County,
Mississippi.]

[Illustration: PLATE 38

_Trionyx spinifer asper_, dorsal views.
_Top_--Left, adult male, TU 15869 (× 1/2), Escambia River, 1.2 mi. E
Century, Escambia County, Florida; right, female, TU 14673.3
(× 1/2), Black Warrior River, 17-1/2 mi. SSW Tuscaloosa,
Tuscaloosa County, Alabama.
_Bottom_--Left, adult male, TU 17117 (× 1/4), Pearl River,
Varnado, Washington Parish, Louisiana; right, female, TU 16584
(× 1/5), locality same as TU 15869.]

[Illustration: PLATE 39

_Trionyx spinifer pallidus_, new subspecies, dorsal views.
_Top_--Juveniles; left, TU 481 (× 2/3), Caddo Lake, Caddo Parish,
Louisiana; right, KU 50832 (× 9/10), mouth of Caney Creek, 4 mi.
SW Kingston, Marshall County, Oklahoma.
_Bottom_--Adult males; left, holotype, TU 484 (× 1/3), locality
same as TU 481; right, TU 1122 (× 2/9), Lacassine Refuge,
Cameron Parish, Louisiana.]

[Illustration: PLATE 40

_Trionyx spinifer pallidus_, new subspecies, dorsal views.
_Top_--Females; left, TU 13213 (× 1/4), Sabine River, 8 mi. SW
Negreet, Sabine Parish, Louisiana; right, TU 13266 (× 2/9),
Sabine River, 8 mi. SW Merryville, Beauregard Parish, Louisiana.
_Bottom_--Left, adult male, SM 2889 (× 1/4), Groveton, Trinity
County, Texas; right, female, TU 14402 (× 1/5), Trinity River,
near junction with Big Creek, Liberty County, Texas.]

[Illustration: PLATE 41

_Trionyx spinifer guadalupensis_, new subspecies, dorsal views.
_Top_--Juveniles; left, ANSP 16717 (× 1), no data; right, KU
50834 (× 1-1/10), Hondo Creek, 4 mi. W Bandera, Bandera County,
Texas.
_Bottom_--Adult males; left, holotype UMMZ 89926 (× 1/3), 15 mi.
NE Tilden, McMullen County, Texas; right, SM 659 (× 3/10),
Colorado River, near Austin, Travis County, Texas.]

[Illustration: PLATE 42

_Trionyx spinifer guadalupensis_, new subspecies, dorsal views.
_Top_--Adult females; left, TU 16036.1 (× 1/5), Llano River,
2 mi. W Llano, Llano County, Texas; right, TU 10160 (× 1/5),
Guadalupe River, 9 mi. SE Kerrville, Kerr County, Texas.
_Bottom_--Left, female, CM 3118 (× 3/4), Black Bayou, Victoria
County, Texas; right, male, TU 14419.6 (× 5/9), San Saba River,
11 mi. NNW San Saba, San Saba County, Texas.]

[Illustration: PLATE 43

_Trionyx spinifer emoryi_, dorsal views.
_Top_--Juveniles; left, UMMZ 69411 (× 3/4), Río Conchos, 9 mi.
N Linares, Nuevo León, México; right, UMMZ 69412 (× 5/6),
Río Purificación, north Ciudad Victoria, Tamaulipas, México.
_Bottom_--Adult males; left, topotype, TU 11561 (× 1/3),
Brownsville, Cameron County, Texas; right, KU 48217 (× 1/3),
Black River Village, Eddy County, New Mexico.]

[Illustration: PLATE 44

_Trionyx spinifer emoryi_, dorsal views. _Top_--Left, adult male,
KU 51194 (× 2/7), Río Conchos, near Meoquí, Chihuahua, México;
right, female, KU 3119 (× 4/9), Salt River, Phoenix, Maricopa
County, Arizona.
_Bottom_--Females; left, KU 3118 (× 1/5), locality same as KU 3119;
right, TU 14453 (× 3/10), Pecos River, near junction with
Independence Creek, Terrell County, Texas.]

[Illustration: PLATE 45

_Trionyx muticus muticus_, juveniles, dorsal views.
_Top_--Topotypes (× 1), Wabash River, 2 mi. S New Harmony, Posey
County, Indiana; left, INHS 7278; right, INHS 7279.
_Bottom_--Left, TU 14375 (× 3/4), Trinity River near junction with
Big Creek, Liberty County, Texas; right, KU 50845 (× 1-2/5),
4 mi. N Atwood, Hughes County, Oklahoma.]

[Illustration: PLATE 46

_Trionyx muticus muticus_, dorsal views.
_Top_--Adult males; left, TU 14606 (× 3/10), White River, Cotter,
Marion County, Arkansas; right, KU 48237 (× 1/3), 8 mi. S
Hanover, Washington County, Kansas.
_Bottom_--Females (× 1/4), 2 mi. E Manhattan, in Pottawatomie
County, Kansas; left, KU 48229; right, KU 48238.]

[Illustration: PLATE 47

_Trionyx muticus calvatus_, dorsal views.
_Top_--Juvenile, TU 17303 (× 1-2/5), Pearl River, Varnado,
Washington Parish, Louisiana.
_Bottom_--Left, adult male, KU 47118 (× 3/10), Pearl River within
4 mi. of Monticello, Lawrence County, Mississippi; right, adult
female, TU 17306 (× 2/9), Pearl River, 9 mi. S Monticello,
Lawrence County, Mississippi.]

[Illustration: PLATE 48

FIG. 1. Habitat of _T. s. pallidus_, Little River, 6.5 mi. S
Broken Bow, McCurtain County, Oklahoma, September 7, 1953.

FIG. 2. Habitat of _T. s. emoryi_, Río Mesquites, 2 mi. W
Nadadores, Coahuila, México, July 27, 1959. Two _emoryi_ were
trapped in hoop nets set in quiet water to left of what is
believed to be a muskrat house.]

[Illustration: PLATE 49

FIG. 1. General habitat of _T. s. pallidus_ and _T. m. muticus_,
Lake Texoma, in a period of low water, 2 mi. E Willis, Marshall
County, Oklahoma, February 24, 1951.

FIG. 2. Type locality of _T. ater_, Tío Candido, 16 km. S Cuatro
Ciénegas, Coahuila, México, July 30, 1959. An adult male of
_T. s. emoryi_ was also netted here.]

[Illustration: PLATE 50

FIG. 1. General habitat of _T. s. asper_ and _T. m. calvatus_,
Escambia River, 2 mi. E, 1/2 mi. N Century, Escambia County,
Florida, June 1, 1954. Three nests of _calvatus_ found on
sand bar in foreground.]

FIG. 2. Nest site of _T. m. calvatus_ (excavated by investigator)
on open sand bar shown above in Fig. 1, June 1, 1954. Note
tracks of turtle in foreground leading toward and away
from disturbed area at left.

[Illustration: PLATE 51

FIG. 1. Eggs of _T. m. calvatus in situ_, June 1, 1954,
approximately six inches below surface, from nest shown in
Fig. 2, Pl. 50. Note sandy substrate and seemingly irregular
arrangement of eggs.

FIG. 2. Eggs of _T. m. calvatus in situ_, June 1, 1954; nest
located at brim of incline shown in foreground of Fig. 1,
Pl. 50. Note gravelly substrate (in foreground) and
symmetrical arrangement of eggs.]

[Illustration: PLATE 52

Lectotype of _Trionyx spinifer_ Lesueur, Museum d'Histoire
Naturelle, Paris, No. 8808 (× 1/5); obtained by C. A. Lesueur
from the Wabash River, New Harmony, Posey County, Indiana.
_Top_--Dorsal view. _Bottom_--Ventral view.]

[Illustration: PLATE 53

Lectotype of _Trionyx muticus_ Lesueur, Museum d'Histoire
Naturelle, Paris, No. 8813 (× 1/2); obtained by C. A. Lesueur
from the Wabash River, New Harmony, Posey County, Indiana.
_Top_--Dorsal view.
_Bottom_--Ventral view.]

[Illustration: PLATE 54

Skull of holotype of _Platypeltis agassizi_ Baur (= _T. s. asper_),
MCZ 37172 (× 1), Savannah River, Georgia.
_Top_--Dorsal view.
_Bottom_--Ventral view.]

28-7818

UNIVERSITY OF KANSAS PUBLICATIONS

MUSEUM OF NATURAL HISTORY

Institutional libraries interested in publications exchange may obtain
this series by addressing the Exchange Librarian, University of Kansas
Library, Lawrence, Kansas. Copies for individuals, persons working in a
particular field of study, may be obtained by addressing instead the
Museum or Natural History, University of Kansas, Lawrence, Kansas. There
is no provision for sale of this series by the University Library, which
meets institutional requests, or by the Museum of Natural History, which
meets the requests of individuals. However, when individuals request
copies from the Museum, 25 cents should be included, for each separate
number that is 100 pages or more in length, for the purpose of defraying
the costs of wrapping and mailing.

* An asterisk designates those numbers of which the Museum's supply (not
the Library's supply) is exhausted. Numbers published to date, in this
series, are as follows:

Vol. 1. Nos. 1-26 and index. Pp. 1-638, 1946-1950.

*Vol. 2. (Complete) Mammals of Washington. By Walter W. Dalquest. Pp. 1-444, 140
figures in text. April 9, 1948.

Vol. 3. *1. The avifauna of Micronesia, its origin, evolution, and
distribution. By Rollin H. Baker. Pp. 1-359, 16 figures
in text. June 12, 1951.

*2. A quantitative study or the nocturnal migration of
birds. By George H. Lowery, Jr. Pp. 361-472, 47 figures
in text. June 29, 1951.

3. Phylogeny of the waxwings and allied birds. By M. Dale
Arvey. Pp. 473-530, 49 figures in text, 13 tables.
October 10, 1951.

4. Birds from the state of Veracruz, Mexico. By George H.
Lowery, Jr., and Walter W. Dalquest. Pp. 531-649, 7
figures in text, 2 tables. October 10, 1951.

Index. Pp. 651-681.

*Vol. 4. (Complete) American weasels. By E. Raymond Hall. Pp. 1-466,
41 plates, 31 figures in text. December 27, 1951.

Vol. 5. Nos. 1-37 and index. Pp. 1-676, 1951-1953.

*Vol. 6. (Complete) Mammals of Utah, _taxonomy and distribution_.
By Stephen D. Durrant. Pp. 1-549, 91 figures in text,
30 tables. August 10, 1952.

Vol. 7. *1. Mammals of Kansas. By E. Lendell Cockrum. Pp. 1-303,
73 figures in text, 37 tables. August 25, 1952.

2. Ecology of the opossum on a natural area in northeastern
Kansas. By Henry S. Fitch and Lewis L. Sandidge. Pp.
305-338, 5 figures in text. August 24, 1953.

3. The silky pocket mice (Perognathus flavus) of Mexico. By
Rollin H. Baker. Pp. 339-347, 1 figure in text.
February 15, 1954.

4. North American jumping mice (Genus Zapus). By Phillip H.
Krutzsch. Pp. 349-472, 47 figures in text, 4 tables.
April 21, 1954.

5. Mammals from Southeastern Alaska. By Rollin H. Baker and
James S. Findley. Pp. 473-477. April 21, 1954.

6. Distribution of Some Nebraskan Mammals. By J. Knox
Jones, Jr. Pp. 479-487. April 21, 1954.

7. Subspeciation in the montane meadow mouse, Microtus
montanus, in Wyoming and Colorado. By Sydney Anderson.
Pp. 489-506, 2 figures in text. July 23, 1954.

8. A new subspecies of bat (Myotis velifer) from
southeastern California and Arizona. By Terry A.
Vaughan. Pp. 507-512. July 23, 1954.

9. Mammals of the San Gabriel mountains of California. By
Terry A. Vaughan. Pp. 513-582, 1 figure in text, 12
tables. November 15, 1954.

10. A new bat (Genus Pipistrellus) from northeastern
Mexico. By Rollin H. Baker. Pp. 583-586. November 15,
1954.

11. A new subspecies of pocket mouse from Kansas. By E.
Raymond Hall. Pp. 587-590. November 15, 1954.

12. Geographic variation in the pocket gopher, Cratogeomys
castanops, in Coahuila, Mexico. By Robert J. Russell
and Rollin H. Baker. Pp. 591-608. March 15, 1955.

13. A new cottontail (Sylvilagus floridanus) from
northeastern Mexico. By Rollin H. Baker. Pp. 609-612.
April 8, 1955.

14. Taxonomy and distribution of some American shrews. By
James S. Findley. Pp. 613-618. June 10, 1955.

15. The pigmy woodrat, Neotoma goldmani, its distribution
and systematic position. By Dennis G. Rainey and Rollin
H. Baker. Pp. 619-624, 2 figures in text. June 10,
1955.

Index. Pp. 625-651.

Vol. 8. Nos. 1-10 and index. Pp. 1-675, 1954-1956.

Vol. 9. 1. Speciation of the wandering shrew. By James S. Findley.
Pp. 1-68, 18 figures in text. December 10, 1955.

2. Additional records and extension of ranges of mammals
from Utah. By Stephen D. Durrant, M. Raymond Lee, and
Richard M. Hansen. Pp. 69-80. December 10, 1955.

3. A new long-eared myotis (Myotis evotis) from
northeastern Mexico. By Rollin H. Baker and Howard J.
Stains. Pp. 81-84: December 10, 1955.

4. Subspeciation in the meadow mouse, Microtus
pennsylvanicus, in Wyoming. By Sydney Anderson. Pp.
85-104, 2 figures in text. May 10, 1956.

5. The condylarth genus Ellipsodon. By Robert W. Wilson.
Pp. 105-116, 6 figures in text. May 19, 1956.

6. Additional remains of the multituberculate genus
Eucosmodon. By Robert W. Wilson. Pp. 117-123, 10
figures in text. May 19, 1956.

7. Mammals of Coahuila, Mexico. By Rollin H. Baker. Pp.
125-335, 75 figures in text. June 15, 1956.

8. Comments on the taxonomic status of Apodemus peninsulae,
with description of a new subspecies from North China.
By J. Knox Jones, Jr. Pp. 337-346, 1 figure in text, 1
table. August 15, 1956.

9. Extension of known ranges of Mexican bats. By Sydney
Anderson. Pp. 347-351. August 15, 1956.

10. A new bat (Genus Leptonycteris) from Coahuila. By
Howard J. Stains. Pp. 353-356. January 21, 1957.

11. A new species of pocket gopher (Genus Pappogeomys) from
Jalisco, Mexico. By Robert J. Russell. Pp. 357-361.
January 21, 1957.

12. Geographic variation in the pocket gopher, Thomomys
bottae, in Colorado. By Phillip M. Youngman. Pp.
363-387, 7 figures in text. February 21, 1958.

13. New bog lemming (genus Synaptomys) from Nebraska. By J.
Knox Jones, Jr. Pp. 385-388. May 12, 1958.

14. Pleistocene bats from San Josecito Cave, Nuevo León,
México. By J. Knox Jones, Jr. Pp. 389-396. December 19,
1958.

15. New subspecies of the rodent Baiomys from Central
America. By Robert L. Packard. Pp. 397-404. December
19, 1958.

16. Mammals of the Grand Mesa, Colorado. By Sydney
Anderson. Pp. 405-414, 1 figure in text, May 20, 1959.

17. Distribution, variation, and relationships of the
montane vole, Microtus montanus. By Sydney Anderson.
Pp. 415-511, 12 figures in text, 2 tables. August 1,
1959.

18. Conspecificity of two pocket mice, Perognathus goldmani
and P. artus. By E. Raymond Hall and Marilyn Bailey
Ogilvie. Pp. 513-518, 1 map. January 14, 1960.

19. Records of harvest mice, Reithrodontomys, from Central
America, with description of a new subspecies from
Nicaragua. By Sydney Anderson and J. Knox Jones, Jr.
Pp. 519-529. January 14, 1960.

20. Small carnivores from San Josecito Cave (Pleistocene),
Nuevo León, México. By E. Raymond Hall. Pp. 531-538, 1
figure in text. January 14, 1960.

21. Pleistocene pocket gophers from San Josecito Cave,
Nuevo León, México. By Robert J. Russell. Pp. 539-548,
1 figure in text. January 14, 1960.

22. Review of the insectivores of Korea. By J. Knox Jones,
Jr., and David H. Johnson. Pp. 549-578. February 23,
1960.

23. Speciation and evolution of the pygmy mice, genus
Baiomys. By Robert L. Packard. Pp. 579-670, 4 plates,
12 figures in text. June 16, 1960.

Index. Pp. 671-690.

Vol. 10. 1. Studies of birds killed in nocturnal migration. By
Harrison B. Tordoff and Robert M. Mengel. Pp. 1-44,
6 figures in text, 2 tables. September 12, 1956.

2. Comparative breeding behavior of Ammospiza caudacuta
and A. maritima. By Glen E. Woolfenden. Pp. 45-75,
6 plates, 1 figure. December 20, 1956.

3. The forest habitat of the University of Kansas Natural
History Reservation. By Henry S. Fitch and Ronald R.
McGregor. Pp. 77-127, 2 plates, 7 figures in text,
4 tables. December 31, 1956.

4. Aspects of reproduction and development in the prairie
vole (Microtus ochrogaster). By Henry S. Fitch. Pp.
129-161, 8 figures in text, 4 tables. December 19,
1957.

5. Birds found on the Arctic slope of northern Alaska.
By James W. Bee. Pp. 163-211, plates 9-10, 1 figure
in text. March 12, 1958.

6. The wood rats of Colorado: distribution and ecology. By
Robert B. Finley, Jr. Pp. 213-552, 34 plates, 8 figures
in text, 35 tables. November 7, 1958.

7. Home ranges and movements of the eastern cottontail
in Kansas. By Donald W. Janes. Pp. 553-572, 4 plates,
3 figures in text. May 4, 1959.

8. Natural history of the salamander, Aneides hardyi. By
Richard F. Johnston and Gerhard A. Schad. Pp. 573-585.
October 8, 1959.

9. A new subspecies of lizard, Cnemidophorus sacki, from
Michoacán, México. By William E. Duellman. Pp. 587-598,
2 figures in text. May 2, 1960.

10. A taxonomic study of the Middle American Snake,
Pituophis deppei. By William E. Duellman. Pp. 599-610,
1 plate, 1 figure in text. May 2, 1960.

Index. Pp. 611-626.

Vol. 11. 1. The systematic status of the colubrid snake,
Leptodeira discolor Günther. By William E. Duellman.
Pp. 1-9, 4 figures. July 14, 1958.

2. Natural history of the six-lined racerunner,
Cnemidophorus sexlineatus. By Henry S. Fitch.
Pp. 11-62, 9 figures, 9 tables. September 19, 1958.

3. Home ranges, territories, and seasonal movements of
vertebrates of the Natural History Reservation. By
Henry S. Fitch. Pp. 63-326, 6 plates, 24 figures in
text, 3 tables. December 12, 1958.

4. A new snake of the genus Geophis from Chihuahua,
Mexico. By John M. Legler. Pp. 327-334, 2 figures
in text. January 28, 1959.

5. A new tortoise, genus Gopherus, from north-central
Mexico. By John M. Legler. Pp. 335-343. April 24, 1959.

6. Fishes of Chautauqua, Cowley and Elk counties, Kansas.
By Artie L. Metcalf. Pp. 345-400, 2 plates, 2 figures
in text, 10 tables. May 6, 1959.

7. Fishes of the Big Blue river basin, Kansas. By W. L.
Minckley. Pp. 401-442, 2 plates, 4 figures in text,
5 tables. May 8, 1959.

8. Birds from Coahuila, México. By Emil K. Urban.
Pp. 443-516. August 1, 1959.

9. Description of a new softshell turtle from the
southeastern United States. By Robert G. Webb.
Pp. 517-525, 2 plates, 1 figure in text.
August 14, 1959.

10. Natural history of the ornate box turtle, Terrapene
ornata ornata Agassiz. By John M. Legler. Pp. 527-669,
16 pls., 29 figures in text. March 7, 1960.

Index Pp. 671-703.

Vol. 12. 1. Functional morphology of three bats: Eumops, Myotis,
Macrotus. By Terry A. Vaughan. Pp. 1-153, 4 plates,
24 figures in text. July 8, 1959.

2. The ancestry of modern Amphibia: a review of the
evidence. By Theodore H. Eaton, Jr. Pp. 155-180,
10 figures in text. July 10, 1959.

3. The baculum in microtine rodents. By Sydney Anderson.
Pp. 181-216, 49 figures in text. February 19, 1960.

4. A new order of fishlike Amphibia from the Pennsylvanian
of Kansas. By Theodore H. Eaton, Jr., and Peggy Lou
Stewart. Pp. 217-240, 12 figures in text. May 2, 1960.

More numbers will appear in volume 12.

Vol. 13. 1. Five natural hybrid combinations in minnows (Cyprinidae).
By Frank B. Cross and W. L. Minckley. Pp. 1-18.
June 1, 1960.

2. A distributional study of the amphibians of the Isthmus
of Tehuantepec, México. By William E. Duellman. Pp.
19-72, pls. 1-8, 3 figures in text. August 16, 1960.

3. A new subspecies of the slider turtle (Pseudemys
scripta) from Coahuila, México. By John M. Legler. Pp.
73-84, pls. 9-12, 3 figures in text. August 16, 1960.

4. Autecology of the copperhead. By Henry S. Fitch. Pp.
85-288, pls. 13-20, 26 figures in text. November 30,
1960.

5. Occurrence of the garter snake, Thamnophis sirtalis, in
the great plains and Rocky mountains. By Henry S. Fitch
and T. Paul Maslin. Pp. 289-308, 4 figures in text.
February 10, 1961.

6. Fishes of the Wakarusa river in Kansas. By James E.
Deacon and Artie L. Metcalf. Pp. 309-322, 1 figure in
text. February 10, 1961.

7. Geographic variation in the North American Cyprinid
fish, Hybopsis gracilis. By Leonard J. Olund and Frank
B. Cross. Pp. 323-348, pls. 21-24, 2 figures in text.
February 10, 1961.

8. Descriptions of two species of frogs, genus Ptychohyla;
studies of American Hylid frogs, V. By William E.
Duellman. Pp. 349-357, pl. 25, 2 figures in text. April
27, 1961.

9. Fish populations, following a drought, in the Neosho and
Marais des Cygnes rivers of Kansas. By James Everett
Deacon. Pp. 359-427, pls. 26-30, 3 figures in text.
August 11, 1961.

10. North American recent soft-shelled turtles (family
Trionychidae). By Robert G. Webb. Pp. 429-611, pls.
31-54, 24 figures in text. February 16, 1962.

Vol. 14. 1. Neotropical bats from western México. By Sydney Anderson.
Pp. 1-8. October 24, 1960.

2. Geographic variation in the harvest mouse,
Reithrodontomys megalotis, on the central great plains
and in adjacent regions. By J. Knox Jones, Jr., and B.
Mursaloglu. Pp. 9-27, 1 figure in text. July 24, 1961.

3. Mammals of Mesa Verde national park, Colorado. By Sydney
Anderson. Pp. 29-67, pls. 1 and 2, 3 figures in text.
July 24, 1961.

4. A new subspecies of the black myotis (bat) from eastern
México. By E. Raymond Hall and Ticul Alvarez. Pp.
69-72, 1 fig. in text. December 29, 1961.

5. North American yellow bats, "Dasypterus," and a list
of the named kinds of the genus Lasiurus Gray. By E.
Raymond Hall and J. Knox Jones, Jr. Pp. 73-98, 4 figs.
in text. December 29, 1961.

6. Natural history of the brush mouse (Peromyscus boylii)
in Kansas with description of a new subspecies. By
Charles A. Long. Pp. 99-110, 1 fig. in text. December
29, 1961.

7. Taxonomic status of some mice of the Peromyscus boylii
group in eastern México, with description of a new
subspecies. By Ticul Alvarez. Pp. 111-120, 1 fig. in
text. December 29, 1961.

More numbers will appear in volume 14.

Vol. 15. 1. The amphibians and reptiles of Michoacán, México.
By William E. Duellman. Pp. 1-148, pls. 1-6,
11 figures in text. December 20, 1961.

2. Some reptiles and amphibians from Korea. By Robert G.
Webb, J. Knox Jones, Jr., and George W. Byers. Pp.
149-173. January 31, 1962.

More numbers will appear in volume 15.

Transcriber's Notes

All obvious typographical error were corrected. Due to variant usage
of hyphens, "soft-shelled" and "crystal-clear" were used as the
standard for variants of those terms. All other variant spellings
of "softshell(s)" and where variant spellings occur in quoted text
or literature titles they were retained. Variants in accented
and non-accented words may exist. Paragraphs split by tables or
illustrations were rejoined.

Typographical Corrections

Page Correction
==== =====================
494 Ordinance School Proving Ground => Ordnance
494 Pl. 12, top => Pl. 42, top
567 Pl. 52, Fig. 2 => Pl. 51, Fig. 2
576 _Agkistrodon piscivorous_ => _piscivorus_
595 Carettochlydae => Carettochelyidae

*** End of this LibraryBlog Digital Book "North American Recent Soft-shelled Turtles (Family Trionychidae)" ***

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